BMI Management During Pregnancy (2019 Update) PDF

CLINICAL PRACTICE 12 GUIDELINE The Management of High or Low Body Mass Index during Pregnancy 2019 Update 2019: Approved by AOM Board of Directors CLINICAL PRACTICE GUIDELINE NO.12 The Management of High or Low Body Mass Index during Pregnancy 2019 Update...

CLINICAL PRACTICE 12 GUIDELINE The Management of High or Low Body Mass Index during Pregnancy 2019 Update 2019: Approved by AOM Board of Directors CLINICAL PRACTICE GUIDELINE NO.12 The Management of High or Low Body Mass Index during Pregnancy 2019 Update AUTHORS (2019) Insurance and Risk Management Program Steering Committee Natalie Hope, MPH ‘Remi Ejiwunmi (Chair), RM Tasha MacDonald, RM, MHSc Abigail Corbin, RM Elana Johnston, RM Carolynn Prior van Fraassen, RM CONTRIBUTORS (2019) Lisa M. Weston, RM Clinical Practice Guideline Committee AOM Staff Megan Bowen, RM Cindy Hutchinson, MSc Elizabeth Cates, RM, PhD Tasha MacDonald, RM, MHSc Shelley Clarke-Dolby, RM Bobbi Soderstrom, RM Meagan Furnivall, RM Genia Stephen (Chair), RM, IBCLC ACKNOWLEDGEMENTS Dana Wilson-Li, RM Kristen Dennis, RM AOM Staff Alexa Minichiello, MSc Ontario Ministry of Health and Long-Term Care Ryerson University Midwifery Education Program Quality Insurance and Risk Management Committee The Association of Ontario Midwives respectfully ‘Remi Ejiwunmi, RM, MSc acknowledges the financial support of the Ministry of Abigail Corbin, RM Health and Long-Term Care in the development of this Ali McCallum, RM guideline. Kim Coultier Holtz, RM The views expressed in this guideline are strictly those AUTHORS (2010) of the Association of Ontario Midwives. No official endorsement by the Ministry of Health and Long-Term Elissa Press, RM Care is intended or should be inferred. Suzannah Bennett, MHSc CONTRIBUTORS (2010) The AOM is committed, through our statement on Gender Inclusivity and Human Rights, to Clinical Practice Guideline Subcommittee reflect and include trans, genderqueer and Elizabeth Darling (Chair), RM, MSc intersex communities in all aspects of our work. Cheryllee Bourgeois, RM This document contains references to sources that Corinne Hare, RM use gendered language to refer to populations of Jenni Huntly, RM pregnant and birthing people. To represent these Paula Salehi, RM sources accurately, we may maintain gendered Lynlee Spencer, RM language. Rhea Wilson, RM We support research and knowledge translation that engages and reflects the entire childbearing population. 2 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index  This guideline reflects information consistent with the best evidence available as of the date issued and is subject to change. The information in this guideline is not intended to dictate a course of action, but to inform clinical decision-making. Local standards may cause practices to diverge from the suggestions within this guideline. If practice groups develop protocols that depart from a guideline, it is advisable to document the rationale for the departure. Midwives recognize that client expectations, preferences and interests are an essential component in clinical decision-making. Clients may choose a course of action that differs from the recommendations in this guideline, within the context of informed choice. When clients choose a course of action that diverges from a clinical practice guideline and/or practice group protocol, this should be well documented in their charts. uncomplicated pregnancy in clients who have a pre- Abbreviations pregnancy body mass index (BMI) less than ( 90 kg for obesity). CPG refers specifically to BMI and the WHO’s BMI (4) Since 2009, the Institute of Medicine (IOM) has used categorization. In an effort to reduce the connotation the World Health Organization (WHO) categorization for that a body with a “normal” BMI (18.5-24.9 kg/m2) BMI, a popular and widely accepted standard (Table 1), and equals a healthy body, this CPG will instead use the it has developed recommendations for gestational weight terminology “recommended BMI.” gain (GWG) based on pre-pregnancy BMI (Table 2). Due to insufficient evidence, the IOM was unable to develop Midwives should keep in mind the limitations of BMI more specific recommendations for gestational weight gain categorization and weight gain recommendations (GWG) among those within obesity classes II and III. (5) when reading this CPG, and when recording BMI and establishing individualized management plans with their BMI is limited by its distinct categorization of clients. 6 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index  Table 1: Obesity and underweight classes as defined by the World Health Organization (10) Obesity classes BMI (kg/m2) Underweight classes BMI Obesity Class I 30-34.9 Severe thinness < 16 Obesity Class II 35-39.9 Moderate thinness 16-16.99 Obesity Class III ≥ 40 Mild thinness 17-18.49 Table 2: Institute of Medicine recommendations for total and rate of weight gain during pregnancy, by pre-pregnancy BMI (5) Rate of weight gain* in Total weight gain Pre-pregnancy BMI BMI (WHO) (kg/m ) 2 second and third trimester range (lbs) (mean range in lbs/wk) Underweight < 18.5 28-40 1 (1-1.3) Recommended weight 18.5-24.9 25-35 1 (0.8-1) Overweight 25.0-29.9 15-25 0.6 (0.5-0.7) Obese (all classes) ≥ 30.0 11-20 0.5 (0.4-0.6) * Calculations assume a 1.1-4.4 lb weight gain in the first trimester (Siga-Ritz, 1994, quoted in (5)) agencies that directly address issues of poverty and RISK FACTORS FOR DEVELOPING marginalization. HIGH OR LOW BMI While genetic and biological factors play a role in Disordered Eating the potential for having a high or low BMI, there Eating disorders such as anorexia nervosa, bulimia are several other important contributing factors that and binge eating disproportionately affect people of differ between populations and among individuals. In childbearing age compared with the general population. particular, research demonstrates that the dramatic rise These disorders are often associated with high or low in obesity in North America can be linked to complex BMI, and they increase the risks of morbidity and interactions between changes to the social, political and mortality. (12) A 2002 survey showed that 1.5% of environmental structure over the past couple of decades. Canadian women aged 15 to 24 years had an eating (11) For example, a limited investment in accessible disorder (13), and that approximately 3% of women infrastructure that promotes healthy practices, coupled will be affected by an eating disorder in their lifetime. with a societal view that idealizes particular bodies, has (14) A review of the literature focused on, and limited an influence on population health and behaviours. (11) to, identifying and monitoring eating disorders and the These issues are heightened for marginalized individuals, most effective treatment interventions from a midwifery demonstrating the importance of social determinants in perspective is available (see Eating Disorders and contributing to health inequities. Women’s Health: An Update (15)). However, an in- depth discussion and critical appraisal of the evidence is The development of equitable policy and infrastructure beyond the scope of this guideline. is required to make significant changes in the rising rates of obesity at the population level. To support clients, midwives may become familiar with and build relationships with community programs and 7 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index RECOMMENDATION Midwives can mitigate and support BMI-related health 1. Offer  referral to the most appropriate and available complications by engaging in thoughtful, informative mental health services for clients who have or are conversations with clients about developing and suspected of having an eating disorder. [III-C] maintaining healthy practices. They can also support clients by connecting them with community health services where appropriate. By using a respectful, informed approach, midwives can identify and PREVENTION OF POOR contribute to clients’ efforts to make positive OUTCOMES behavioural changes while remaining mindful that The information presented below is a summary of the causes of high or low BMI often extend beyond an prevention or intervention strategies that reduce the individual’s control. Midwives should reflect on their risks in pregnancy due to an elevated or decreased BMI. own beliefs about individuals with a high- or low-BMI, Ultimately, midwives should discuss individualized care and they should take care not to perpetuate harmful plans with clients, tailored to their specific needs, while assumptions about clients’ health, eating habits, lifestyle accounting for individual, social and environmental choices or physical ability. realities that may affect their clients’ ability to achieve and maintain their goals. RECOMMENDATION 2. Discuss  the benefits of optimizing GWG in Optimizing Gestational Weight Gain pregnancy for clients with a BMI < 18.5 kg/m2 or ≥ A 2017 systematic review and meta-analysis of 23 cohort 30 kg/m2. [II-2-B] [new 2019] studies and 1 309 136 participants found that individuals who gain weight within the recommended ranges SUMMARY STATEMENT outlined in Table 2 have better pregnancy outcomes For clients with a BMI ≥ 30 kg/m2, consider discussing than those who do not. This suggests that complications the benefits of achieving a recommended BMI prior to related to obesity or underweight can be reduced or the next conception. [new 2019] prevented through the careful management of weight gain during pregnancy. Compared with those who gained weight within the guidelines, regardless of BMI Charting Weight Gain on Antenatal Records category pre-pregnancy, GWG below the guidelines was The IOM recommends documenting preconception BMI associated with an increased risk for small for gestational as well as subsequent weight gain throughout pregnancy age (SGA) (OR 1.53 95% CI 1.44-1.64) and preterm birth and sharing these results with clients so they are aware (OR 1.70 95% CI 1.32-2.20), with the greatest risk among of their progress toward their weight gain goals. (5) participants who were underweight pre-pregnancy. In Midwives who choose to chart weight gain may be able contrast, gaining weight above the guidelines, regardless to help their clients address excessive or inadequate of BMI category pre-pregnancy, increases the risk for GWG during pregnancy. Research from a longitudinal large for gestational age (LGA) (> 90th percentile; OR birth cohort study demonstrates that participants 1.85 95% CI 1.76-1.95), macrosomia (> 4500 g; OR 1.95 who inaccurately estimated their pre-pregnancy body 95% CI 1.79-2.11) and caesarean delivery (OR 1.30 95% weight were more likely to gain excessive gestational CI 1.25-1.35). (16) Although the IOM recommendations weight, with the greatest likelihood of excessive gain may provide a general reference for GWG, this among individuals who were overweight/obese and who research is largely based on observational data. There underestimated their true pre-pregnancy weight (OR 7.6 is also insufficient evidence to report on other adverse 95% CI 3.4-17.0). (17) outcomes, including preeclampsia and gestational diabetes, which are more common in pregnant people When discussing weight charting and management, with a high BMI. Until more evidence is available, clients in particular with high-BMI individuals, research should not rely on specific weight gain targets, but rather shows that careful wording is important to developing focus on optimizing GWG by maintaining a healthy diet a healthy, respectful relationship between client and and physical activity. clinician. Midwives should avoid such negative terms 8 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index as “fat,” “fatness,” “large size,” “heaviness” and “obesity” However, the researchers could not describe the with high-BMI clients, as these may be interpreted “optimal” pregnancy diet based on their results. (22) as offensive or distressing and could prevent further This is consistent with research that failed to find discussion on this topic. (18) Rather, “weight,” “excess significant associations between particular foods and weight” and “BMI” are more likely to be interpreted as excessive GWG or inadequate weight gain across all neutral or desirable. (18)Midwives should encourage participants. (23) Although most clients will likely open discussion and questioning, and they should benefit from the general dietary advice in Canada’s respect the wishes of clients who have specific Food Guide, midwives may also refer clients to preferences about the language they prefer their provider nutritionists for specific, individualized direction. A to use. Clients should also be given the opportunity to systematic review on this topic suggests that social discuss any challenges with weight management, and support, knowledge about healthy foods, the skills to midwives should respond with appropriate assistance. prepare meals and the ability to eat at home enabled healthy habits during pregnancy. Cravings, nausea In some cases, midwives or clients may choose not to and schedule demands have been observed as barriers routinely measure or document weight gain. Midwives to healthy eating. (24) Therefore, the appropriate diet can offer to have an informed choice discussion about for each client should take into account individual the benefits and risks of charting weight gain for clients preferences and experiences during pregnancy, time with a BMI < 18.5 kg/m2 or ≥ 30 kg/m2. and budget constraints, cultural practices, and food knowledge and preparation skills. (22) The risks and benefits of charting GWG for clients in the recommended BMI category are outside the scope of this According to the 2018 Canadian Guideline for guideline. Physical Activity throughout Pregnancy, developed by the Society of Obstetricians and Gynaecologists (SOGC), exercise during pregnancy is associated with RECOMMENDATION improved cardiovascular function and a reduction 3. Midwives  may consider calculating and of the occurrence of excess weight gain. (19,25) The documenting pre-pregnancy BMI on the first 2018 SOGC guideline recommends that pregnant antenatal record. If pre-pregnancy weight is people should try to do physical activity at least three unknown, midwives may consider documenting days a week, and they should incorporate a variety of BMI at the intake visit. [III-B] [new 2019] exercises, including aerobic exercise, resistance training, gentle stretching and pelvic floor training. (26) Low- Nutrition and Physical Activity in Pregnancy risk, previously active individuals can continue their CClients may be offered services for counselling related exercise routines. (26) Research demonstrates that a to nutrition and physical activity to help them achieve sedentary lifestyle during pregnancy may be associated their GWG goals. These behavioural interventions can with adverse outcomes, including loss of muscular improve long-term health, optimize infant birth weight and cardiovascular fitness, excessive GWG, higher risk and help reduce childhood obesity. (5) However, there of gestational diabetes or hypertensive disorders of is a lack of good evidence to guide clinical practice on pregnancy, varicose veins and deep vein thrombosis, how to support clients to meet their weight gain goals a higher incidence of complaints for conditions such during pregnancy, specifically which interventions are as dyspnea or lower back pain, and poor psychological the most effective. (5) Unfortunately, the ideal format adjustment to the physical changes of pregnancy. (26) and intensity of methods to limit GWG for high-BMI pregnant people has not been established. (5, 19-21) Despite the important benefits of physical activity during pregnancy, midwives should be aware that vigorous A 2018 systematic review and meta-analysis on activity (30 minutes/day) is a significant predictor of attenuating pregnancy weight gain discovered that inadequate weight gain during pregnancy for clients with dietary interventions have demonstrated effectiveness a low-BMI (OR 0.76, 95% CI 0.60-0.96, p = 0.005) (27). in reducing excessive weight gain during pregnancy. 9 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index Most available research on weight management describes midwives will care for more individuals with a high interventions designed for the general population, BMI. Midwives should possess the knowledge and but the best practices identified are transferable to skills to manage the clinical outcomes associated with encourage healthy behaviour changes in pregnant a high BMI, and be aware that clients with a high BMI people. Research demonstrates that participants achieve often experience stigmatization and weight bias from greater improvements in health outcomes when the medical professionals. Thus, midwives should make weight management approach is multifaceted. (28) Thus, every effort to adapt their care to promote a helpful, an individualized plan that incorporates both diet and healing environment and support a normal birth physical activity while taking into account individual experience. Such accommodations should include the experiences and knowledge, social support, resource use of appropriately sized medical equipment, barrier- constraints, medical contraindications and referrals to free washrooms in midwifery clinics, and any necessary appropriate health care providers will more likely result consultation or collaboration with other medical and in optimal GWG. health care professionals. (31) RECOMMENDATIONS ANTENATAL AND INTRAPARTUM COMPLICATIONS: HIGH BMI 4. All  clients should be counselled about the importance of good nutrition and physical activity High BMI is associated with possible complications during pregnancy. Canada’s Food Guide is an throughout pregnancy, as described in Tables 4a, 4b, 4c, example of a nutrition guideline that includes 5a, 5b, and 5c. The values listed are an accumulation of dietary advice for individuals who are pregnant or the available research contained in meta-analyses and/ nursing. [II-2-B] or systematic reviews from 2010 to 2018. The reported ORs and RRs are subject to error, as researchers often fail 5. For  clients with a BMI < 18.5 kg/m2 or ≥ 30 kg/m2, to adjust for the limitations of BMI, GWG, underlying midwives should identify and offer referrals to the comorbidities and social/environmental characteristics most appropriate health care providers available in across studies. This raises the likelihood of confounding clients’ communities to discuss nutrition, healthy and potentially overestimating the independent risks eating and other good habits. [II-2-B] of high BMI during pregnancy. Studies with high-BMI populations may also use different sample selection and analysis techniques that may not be generalizable for HIGH BMI Ontario. The following research into risk factors should therefore be interpreted with caution. The worldwide prevalence of obesity has risen dramatically in the past few decades. In 2017, self- reported weight and height data from Statistics Canada Table 3: Strength of OR/RR values observed an obesity rate (BMI ≥ 30 kg/m2) of 26.9% OR/RR Strength of risk factor for Canadians aged 18 and over. (3) More specifically, ≤ 2.99 Mild the percentage of people aged 18 to 34 who were 3.00-5.99 Moderate considered obese increased from 17.3% in 2015 to 19.7% in 2017. (30) As the prevalence of obesity increases, ≥ 6.00 Strong 10 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index  Table 4a: Antenatal/intrapartum complications: BMI ≥ 30 kg/m2 compared with a BMI of 18.5-24.9 kg/m2 Complication(s) OR/OR range Mild risk factor Miscarriage 1.26-1.31 (33,34) Antenatal anxiety 1.41 (34) Antenatal depression 1.43 (34) Caesarean section 2.01-2.05 (34,35) Moderate risk factor Preeclampsia 3.15 (36) Gestational diabetes 3.34-3.76 (34) Table 5a: Antenatal/intrapartum complications: BMI ≥ 40 kg/m2 compared with a BMI of 18.5-24.9 kg/m2 Complication(s) OR/RR range Moderate risk factor Induction of labour 3.66 (35,37) Preeclampsia 3.80 (37) Gestational diabetes 5.20 (37) Research consistently demonstrates that the risk for When assessing and monitoring clients’ blood pressure, antepartum and intrapartum health complications it is critical that midwives utilize the appropriately increases as BMI increases. In particular, numerous sized blood pressure cuff. Blood pressure in high-BMI systematic reviews and observational studies have individuals may be overestimated when cuff sizes are too demonstrated a step-wise increase in the risks for small, leading to over-diagnosis of hypertension. (52) hypertensive conditions and preeclampsia (5,38–49) and gestational diabetes mellitus (GDM). (34,37,50) National The use of low-dose acetylsalicylic acid (ASA) (optimal guidelines on obesity and pregnancy have acknowledged dosage is unknown but may be between 60 and 150 these increased risks, and they recommend that clients g) (53) during pregnancy has been shown to provide be well informed and monitored closely, particularly if some preventive benefit for multiple adverse pregnancy they have other risk factors. (51) outcomes, including preeclampsia and hypertension. (54) Some guideline groups have recommended low- dose ASA for clients with a high-BMI, but only for Preeclampsia and Hypertension those with at least one other moderate risk factor for A recent meta-analysis of approximately 1.4 preeclampsia. (51,54) Other moderate risk factors million people found a moderately increased risk include age > 40 years, family history of preeclampsia of preeclampsia in pregnant individuals with a BMI and current multiple pregnancy. (51) To learn more ≥ 30 kg/m2 compared with individuals within the about the management of preeclampsia with low-dose recommended BMI range (OR 3.15, 95% CI 2.96-3.35). ASA, and for further discussion on the relationship (36) A separate meta-analysis found that the risk of between hypertensive disorders during pregnancy and preeclampsia for those with a BMI ≥ 40 kg/m2 was high BMI, refer to the AOM’s CPG No. 15: Hypertensive moderate (OR 3.80, 95% CI 3.07-4.68), even when Disorders of Pregnancy. (55) potentially confounding risk factors were controlled for. (37) 11 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index RECOMMENDATION limited systematic research on this association. While 6. Obtain  and document a baseline blood pressure, a 2016 meta-analysis determined that there is a using the appropriate cuff size for clients with a BMI mild risk for postpartum venous thromboembolism ≥ 30 kg/m2. [II-2-B] among those with a BMI ≥ 30 kg/m2 (OR 2.5, 95% CI 1.8-3.5) (see Table 4b) and a moderate risk among individuals with a BMI ≥ 40 kg/m2 (OR 4.6, 95% CI Gestational Diabetes 3.0-7.2) (see Table 5b) (58), a 2014 systematic review The link between GDM and high BMI was identified three studies with varied results on the risk demonstrated in a recent overview of systematic of antepartum venous thromboembolism in the BMI reviews, in which a moderately increased risk of ≥ 30 kg/m2 population (59). Of these three studies, developing GDM was found in two meta-analyses one found a strong risk (OR 9.7) for antepartum among those with a BMI ≥ 30 kg/m2, compared with venous thromboembolism among individuals with a individuals within the recommended BMI range (see BMI ≥ 30 kg/m2, while the other two studies found no Table 7a). (34) Despite the known association between significant risk for those with a BMI ≥ 30 kg/m2. (59) obesity and GDM, an updated Cochrane review Despite this variation, clinical practice guidelines on reported insufficient evidence to support the use of obesity and pregnancy – including those developed by GDM screening based on risk factors (e.g., BMI ≥ 30 SOGC 2010 and the American College of Obstetricians kg/m2) over universal screening. (56) This is consistent and Gynecologists (ACOG) 2015 – acknowledge the with the AOM’s 2016 literature review on GDM, which increased risk of venous thromboembolism throughout concludes that there remains significant uncertainty and after pregnancy, particularly if other risk factors are and disagreement as to whether all clients should be present. (51) The Royal College of Obstetricians and screened for GDM, or only select clients with specific Gynecologists (RCOG) reports several risk factors for risk factors. (57) Although the AOM does not outline venous thromboembolism that should be accounted for a specific screening approach, it provides an overview when considering thromboprophylaxis, including BMI of the current evidence and recommendations from ≥ 30 kg/m2, planned caesarean section, age > 35 years several other guideline development groups, all of and medical comorbidities. (60) Moreover, the RCOG which identify BMI ≥ 30 kg/m2 as a risk factor for recommends offering postnatal thromboprophylaxis to GDM. (57) all pregnant people with a BMI ≥ 40 kg/m2, regardless of their mode of delivery. (61) However, given the paucity Research suggests that the risks for adverse perinatal of high-quality evidence on when and in what form outcomes associated with GDM are likely due to thromboprophylaxis should be considered with high- hyperglycemia and the pregnant person’s coexisting BMI clients (62), the necessity of this treatment should environment, rather than high BMI, and that well- be individually assessed, taking into account the full controlled glucose levels of the pregnant person appear clinical picture. This is consistent with current guidance to decrease the occurrence of adverse outcomes. (57) from the SOGC. (62) Midwives may refer to the AOM’s literature review on GDM for more information on this topic. RECOMMENDATION 8. Midwives  should individually evaluate each client’s RECOMMENDATION need for thromboprophylaxis. They may consider 7. For  clients with a BMI ≥ 30 kg/m2, midwives should suggesting an antepartum consultation with a discuss the higher risk of preeclampsia and GDM, physician for clients with a BMI ≥ 40 kg/m2, or for along with the risks and benefits of GDM screening. clients with a BMI ≥ 30 kg/m2 and other known risk [II-2-A] [new 2019] factors for thromboembolism. [III-C] [new 2019] Thromboembolism Fetal Monitoring Although thromboembolism is reported by other Excessive abdominal adiposity may affect midwives’ clinical guideline development groups as a serious ability to monitor fetal development during pregnancy health risk during high-BMI pregnancies, there is 12 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index  through ultrasound and abdominal palpation. (45) effect on the accuracy or reliability of abdominal A review of 11 019 pregnancies found that the rate of fetal electrocardiograms during labour for pregnant suboptimal visualization of fetal cardiac structures participants with high BMI; therefore, midwives may through ultrasound increased 49.8% and craniofacial consider this method when fetal heart rate is difficult to structures increased 31% in individuals with a BMI ≥ detect. (66) 30 kg/m2 compared with those having a BMI < 30 kg/ m2. (63) Midwives may also find abdominal palpation RECOMMENDATIONS and symphysis-fundal measurements more difficult to 9. For  second-trimester ultrasounds indicating interpret in clients with high BMI, as growth charts may suboptimal visualization, discuss limitations of not be accurate for this group. (64) ultrasound with client and consider offering repeat ultrasound if needed. [III-B] Although fetal heart rate (FHR) monitoring with a Pinard stethoscope or a Doppler ultrasound may 10. W  hen abdominal palpation proves challenging and/ be challenging with high-BMI clients, there is no or symphysis-fundal measurements are unreliable, evidence to support the necessity of continuous FHR midwives should discuss the risks and benefits of a monitoring during labour on the basis of high BMI third-trimester ultrasound and offer as necessary to alone. (65) Research from 2014 reported no detrimental address any information gaps. [II-2-B] Bariatric Surgery and Pregnancy Bariatric surgery is performed on people who have a very high BMI. Weight loss is usually achieved with a medical device (gastric banding) or gastric bypass. The majority of bariatric surgery patients are people of childbearing age. (124) In 2007, 1313 surgeries were performed in Canada, with 6783 patients on waiting lists. (125) The most popular surgeries are laparoscopic adjustable gastric band (LAGB) and Roux-en-Y gastric bypass (RYGB), which reduce the size of the stomach. Surgeries that bypass all or part of the small intestine result in food restriction and malabsorption and increase the risk of nutritional deficiencies. (126,127) Evidence on pregnancy outcomes after bariatric surgery is growing but limited, and includes case reports, case-control and cohort studies. For pregnant individuals who have had gastric bypass, folate, iron and B12 malabsorption and deficiencies may occur. (128) Close monitoring may be particularly important with respect to their nutritional status. (127) GDM testing may require alternate methods, as use of standard glucose solutions can cause rapid gastric emptying. Sugar consumption may cause cramping, diarrhea, hypotension, nausea or tachycardia. Midwives may consider measuring fasting serum glucose periodically, or a referral to a physician for a three-day continuous glucose sensor. While these methods do not supersede traditional oral glucose screening, they might be better tolerated by those who have had bariatric surgery. (128) People whose weight has stabilized and who maintain good nutritional balance throughout their pregnancies may experience less morbidity and mortality than they would have with obesity. Small studies have shown that individuals who have had bariatric surgery have lower risks of preeclampsia, LGA infants, GDM, fetal macrosomia and hypertension disorders. (126,129) In a retrospective study of 808 participants who had surgery before and after delivery, the surgery was independently associated with a reduced risk of diabetes, hypertensive disorders and fetal macrosomia. (130) Individuals who have had bariatric surgery may be at increased risk of abdominal hernias, gallstones, changes in metabolism (including metabolism of medications), organ displacement as the uterus enlarges, and possible increased risk of intrauterine growth restriction (IUGR). (127) Clients should be encouraged to breast- or chest-feed postpartum. It is important to note, however, that there are limited case reports of nutritional deficiency in the infants of parents who have had gastric bypass, even if the parent is asymptomatic. (131) More research is needed to compare pregnancy complications by the type of surgery. (132) 13 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index SUMMARY STATEMENT epidural needles can generally be used. (68) If pain relief Midwives may consider offering continuous fetal heart is requested or necessary for clients with high BMI, it rate monitoring to clients with a high-BMI in whom would be ideal to discuss potential complications with fetal heart rate is difficult to detect using intermittent them prior to labour. auscultation. [new 2019] RECOMMENDATION Anesthesia 11. Midwives  should consider offering an antepartum There are reports in the literature of increased difficulties anesthesiology consultation for clients who plan to with placing epidural or spinal catheters and with have an epidural, or for those who wish to have a intubation among individuals with high BMI. (39,67,68) more detailed discussion about potential anesthesia As well, the risk of dural puncture may be greater for complications related to BMI ≥ 30 kg/m2. [III-C] individuals with high BMI. However, BMI is a poor predictor of distance to the epidural space, and standard POSTPARTUM CONSIDERATIONS: HIGH BMI Table 4b: Postpartum complications: BMI ≥ 30 kg/m2 compared with a BMI of 18.5-24.9 kg/m2 Complication(s) OR/OR range Mild risk factor Postpartum depression 1.30 (34) Surgical or caesarean wound infection 1.00-2.10 (34) Postpartum venous thromboembolism 2.5 (58) Postpartum hemorrhage 1.2* (69) Mild to moderate risk factor Not initiating breast or chest feeding 1.19-3.65 (34) Table 5b: Postpartum complications: BMI ≥ 40 kg/m2 compared with a BMI of 18.5-24.9 kg/m2 Complication(s) OR/RR Mild risk factor Postpartum hemorrhage 1.43* (69) Moderate risk factor Postpartum venous thromboembolism 4.6 (58) Surgical or caesarean wound infection 5.94 (37) *OR value was obtained from a meta-analysis published in 2008. No applicable meta-analyses or systematic reviews that examined risk of postpartum hemorrhage were published in 2010-2018. Weight Retention and Mental Health after pregnancy may be linked to postpartum depression. Compared with individuals within the recommended (34) To better understand this association, qualitative BMI range, individuals with obesity are more likely to studies speculate that stigma and judgment associated experience weight retention post-pregnancy. (5,70–71) with obesity, criticisms from health care providers and Research suggests that excessive weight gain during and lack of available social supports may all contribute to 14 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index the increased risk of poor mental health for postpartum Lactation parents with high BMI. (73) However, these findings Those with a BMI ≥ 30 kg/m2 are less likely to initiate cannot be used to determine a direction of association, human milk feeding and they have been shown to have since those with poor mental health may also struggle a shorter duration of nursing (both exclusive and any), with weight management. (34) regardless of GWG. (34,75–79) The precise reason for this association is unclear, but it may be due to a decreased prolactin response to suckling (which would Caesarean Wound Infection in turn reduce milk production), a delay in lactogenesis, There appears to be a moderate risk for surgical or or large breasts that may increase the difficulty of caesarean wound infection among postpartum parents latching. (34,75) with a BMI ≥ 40 kg/m2, even when other risk factors are controlled for (AdjRR 5.94, 95% CI 2.98-11.77). (37) Midwives can play a vital role in encouraging chest/ However, research on the risk for surgical or caesarean breastfeeding by discussing the numerous benefits for wound infection among those with a BMI ≥ 30 kg/m2 is both parent and newborn and by providing lactation inconclusive, with some studies reporting a mild risk and support. Midwives should also address any concerns of others reporting none. (34) Research in this area comes to clients who choose not to nurse. little consensus on the factors that contribute to surgical site infection, but factors may include length of surgery, use of prophylactic antibiotics, skin closure technique RECOMMENDATION and comorbidities such as diabetes. (74) Moreover, 12. M  idwives are well suited to help clients with a BMI inconclusive results among those with a BMI ≥ 30 kg/ ≥ 30 kg/m2 who may experience difficulties with m2 may be related to limitations of the BMI value, which nursing to establish good positioning, latch and milk does not provide an exact measure of excess fat or fat supply. When appropriate, midwives should refer distribution. Indeed, not all individuals with a BMI ≥ 30 clients to a lactation consultant or other specialist kg/m2 have high levels of excess fat around their abdomen, for lactation support. [III-B] but those with excess abdominal fat may be more likely to experience friction, sweat and bacteria buildup around the surgical site, thus increasing their risk for infection. FETAL AND NEONATAL COMPLICATIONS: HIGH BMI Table 4c: Fetal and neonatal complications: BMI ≥ 30 kg/m2 compared with recommended BMI 18.5-24.9 kg/m2 Complication(s) OR/OR range Negligible to mild risk factor Preterm birth (< 37 weeks) 1.05-1.23 (34,80) Mild risk factor Congenital heart defects 1.17 (81) Orofacial clefts 1.18 (82) Infant death (≤ 1 year old) 1.42 (83) Preterm birth (> 32 weeks) 1.59 (34) Stillbirth 1.63-2.07 (34,80) Neural tube defects 1.68-1.87 (34,84) NICU admission 1.91 (80) Large for gestational age (> 90th percentile) 1.88-2.42 (80,85,86) 15 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index  Macrosomia (> 4000 g) 2.00-2.92 (80,85,86) Mild to moderate risk factor Macrosomia (> 4500 g) 2.77-3.23 (85,86) Moderate risk factor Childhood obesity 3.06 (86) Table 5c: Fetal and neonatal complications: BMI ≥ 40 kg/m2 compared with recommended BMI 18.5-24.9 kg/m2 Complication(s) OR/RR Mild risk factor Congenital birth defects 1.46 (37) Preterm birth (< 37 weeks) 1.50 (34) Stillbirth 2.19 (34) Preterm birth (< 32 weeks) 2.27 (34) Moderate risk factor Large for gestational age (> 90th percentile) 3.14 (37) Large for Gestational Age and Macrosomia review and meta-analysis of 22 studies found a pooled LGA fetuses (> 90th percentile) and fetal macrosomia OR for NTDs of 1.68 (95% CI 1.51-1.87, p < 0.00001) (> 4000 g or > 4500 g) are more common in pregnancies among those with pre-pregnancy BMI ≥ 30 kg/m2 with individuals who have a BMI ≥ 30 kg/m2 and a compared with those within the recommended BMI BMI ≥ 40 kg/m2 (see Table 4c and 5c). (40,44,45,87–90) range. (84) Macrosomia is associated with an increased risk of shoulder dystocia, birth injury and perinatal death, The reasons that individuals with high BMI may as well as an increased risk of caesarean delivery. be at increased risk for NTDs are not entirely clear. (63) It is important to note that after adjusting for Researchers have suggested that lower fruit and vegetable fetal macrosomia, obesity during pregnancy is not an consumption, overall increased energy intake, higher independent risk factor for shoulder dystocia. (39,91,92) metabolic demands or a high-glycemic index diet may be more prevalent in this population, decreasing folate availability thereby increasing the risk of NTDs. (95) SUMMARY STATEMENT Recent pharmacokinetic research further elucidates the Clients with a BMI ≥ 30 kg/m2 would benefit from relationship between high BMI and NTDs. Evidence informed choice discussions about the increased risk from one 2013 study demonstrated that women of for fetal macrosomia and LGA, and the associated childbearing age with high BMI versus recommended complications this may have during labour and birth. BMI had different pharmacokinetic responses to an [new 2019] equivalent dosage of folic acid administered after a period of fasting. (96) In this study, the maximum serum Neural Tube Defects and Folate Intake folate concentration was 34% lower in the high-BMI Since the introduction of mandatory folic acid group compared with recommended BMI individuals, fortification of flour in 1997, there has been a dramatic even though the rate of dietary folate absorption between 46% decrease in neural tube defects (NTDs) in Canada. the groups was the same, indicating that excess body (93) However, evidence indicates that the risk for NTDs fat may influence folate circulation into tissue. (96) remains especially elevated among individuals with high This finding is consistent with a 2017 systematic review, BMI, even since fortification. (94) A 2016 systematic which found that the negative association between 16 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index Folic Acid and Folate Folic acid is a stable synthetic form of folate that is routinely added to supplements, drugs and fortified foods. (133) Once ingested, folic acid must undergo several metabolic steps to be converted into a biologically active tetrahydrofolate (THF) form. (133) Supplementation of folic acid during pregnancy is widely considered safe, and doses up to 5.0 mg have not been known to have adverse effects on pregnant people or fetuses. (134) Some researchers have raised concerns about potential adverse effects of excessive folic acid consumption, but these results are largely inconsistent, and further research with high-BMI individuals is required. (135) Folate may also be increased through diet, in the form of 5-methyltetrahydrofolate (5-MTHF), which naturally occurs in food and is the most abundant derivative of folate found in the blood. (136) Because 5-MTHF is already biologically active, it requires no further metabolism to be absorbed within the body. (133) Although most individuals can properly convert folic acid into its active form, this process is disrupted for those with a MTHFR (methylenetetrahydrofolate reductase) genetic mutation. (136) A body of research studying participants within the recommended BMI finds that supplementation with 5-MTHF is equally or more effective when compared with folic acid for increasing folate concentration in the blood in individuals with and without the MTHFR mutation. (136–139) Supplemental forms of 5-MTHF may be safely used as an alternative to folic acid for people within the recommended BMI. However, this research has yet to be replicated among individuals with a high BMI, and thus the efficacy of 5-MTHF for this specific population is currently unknown. serum folate concentration and BMI remained even after CI 0.22-0.89). Considering that high-BMI individuals adjustment for folate intake. (97) exhibit lower serum folate levels than recommended BMI individuals, and that the metabolism of folate This evidence suggests that a proportion of the NTD risk may differ with adiposity, it is possible that high-BMI associated with pre-pregnancy high-BMI status may be participants in this sample were not administered explained by a decreased concentration of serum folate adequate levels of folic acid to ensure a protective effect in the blood. (96-98)Since nutrients for the developing against NTDs. (99) embryo are derived from the pregnant person’s serum and folate requirements are higher during pregnancy, Research that has adjusted for the consumption of folate limited folate availability may affect the development based on BMI has found reductions in NTDs comparable of the fetus. Individuals with high BMI may require to those of recommended BMI individuals. (95,96.99) a higher dosage of supplemental or dietary folate to Evidence from one case-control study in 2013 assessed achieve a serum folate concentration that provides the impact of higher intake of dietary folate in individuals protection against NTDs. (99) with high BMI. In the study, overweight (BMI 25.0-29.9 kg/m2) and obese (BMI ≥ 30 kg/m2) participants who One case-control study found that individuals within consumed 0.45-3.12 mg of dietary folate daily during the the recommended BMI range (18.5-24.9 kg/m2) periconceptional period significantly reduced their risk who supplemented daily with 0.4 mg of folic acid in of NTD-affected pregnancies (aOR 0.28 95% CI 0.10- the periconceptional period (three months before 0.76). (95) This research suggests that the NTD risk in conception and three months after conception), individuals with high BMI may be attenuated to some demonstrated a significantly reduced risk for NTDs in degree with a folate-rich diet. Foods rich in naturally comparison to recommended BMI individuals who did occurring folate include asparagus, broccoli, spinach, not supplement with folic acid (aOR 0.21, 95% CI 0.11- lentils, beans and liver. (100) 0.40). The risk for NTDs was also reduced among high- BMI individuals who were supplemented with folic acid, Currently, there is no clear consensus in available but this reduction was not as large when compared with literature and among clinical guideline groups on the that of recommended BMI individuals (aOR 0.65, 95% specific recommended dosage of folate or folic acid for 17 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index pregnant clients with a BMI ≥ 30 kg/m2. Consistent RECOMMENDATION with the above literature, the RCOG 2010 and the Royal 14. M  idwives should ensure that they feel competent to Australian and New Zealand College of Obstetricians perform venipuncture and gain IV access in clients and Gynecologists (RANZCOG) 2013 recommend a with a BMI ≥ 30 kg/m2, and they may consider high dose folate supplement of 5 mg/day for clients with establishing IV access during labour in clients who a BMI ≥ 30 kg/m2; ideally given before pregnancy and choose home birth. [III-C] with continuance through the antenatal period. (61,101) Health Canada guidance from 2010 recommends that Choice of Birthplace all pregnant people supplement with 0.4 mg of folic A 2013 analysis of data from the Birthplace in England acid regardless of BMI, but after considering the above national prospective cohort study examined the risk research it remains unclear if this dosage is high enough of adverse outcomes among pregnant individuals with to provide a protective effect for individuals with obesity. high BMI who planned to give birth at home, in a (99,102) Although a folate/folic acid dosage ranging Freestanding Midwifery Unit (FMU) or in an Alongside from 0.4 mg to 5 mg is likely to provide some preventive Midwifery Unit (AMU). (104) The participants selected benefit for high-BMI clients, more research is needed for this analysis were considered “otherwise healthy,” to recommend a specific dosage that provides the most meaning that before the onset of labour they were not optimal preventive effect against the development of known to have any medical or obstetric history risk NTDs for high-BMI clients. factors, according to the National Institute for Health and Care Excellence (NICE) intrapartum care guideline, RECOMMENDATION other than BMI > 35 kg/m2. Risk factors as identified 13. F  or clients with a BMI ≥ 30 kg/m2, midwives by NICE include various chronic diseases as well as a should discuss the benefits of a diet high in history of previous pregnancy-related complications, nutrient-dense, folate-containing foods before and such as caesarean section, uterine rupture and eclampsia during pregnancy to reduce the risk of NTDs. For (for a detailed list of risk factors, see Tables 2 and 3 in the clients who cannot maintain a high-folate diet, Appendix). (105) The results of this study determined midwives may also discuss the risks and benefits of that when birth occurred at home, those with a BMI of administering a supplement with 0.4 mg to 5 mg of 30-35 kg/m2 (obese) and those with a BMI ≥ 40 kg/m2 folic acid. [II-2-B] [new 2019] (very obese) did not significantly differ from participants within the recommended BMI range (18.5-24.9 kg/m2) in their risks for neonatal unit admission or intrapartum MIDWIFERY-SPECIFIC stillbirth/early neonatal death (AdjRR 1.36, 95% CI CONSIDERATIONS: HIGH BMI 0.80-2.29 for obese; AdjRR 1.17, 95% CI 0.49-2.81 for very obese), or in their risks for obstetric interventions Establishing IV Access and adverse maternal outcomes (AdjRR 1.04, 95% CI Visualization and palpation of a suitable vein for IV 0.89-1.22 for obese; AdjRR 0.95, 95% CI 0.59-1.52 for cannulation may be more challenging in clients with a BMI very obese). As with those who gave birth at home, no ≥ 30 kg/m2. This is due to thicker subcutaneous adipose significant differences in risk were found between high- tissue, which can result in smaller, more superficial veins BMI and recommended-BMI participants who opted for that often have more valves and bifurcations. (103) In the a birth in an FMU or an AMU. (104) event of an emergency, midwives may find establishing an IV line in the high-BMI client difficult. Therefore, midwives Similar results were found in a 2018 national prospective may consider placing an IV during labour, particularly for a cohort study, which examined the risks for adverse planned home birth. intrapartum and neonatal complications among individuals with a BMI of 35.1-40 kg/m2 in comparison with recommended-BMI individuals (18.5-24.9 kg/ m2) who were admitted to give birth in an AMU. As with the last study, all participant data was adjusted for confounding risk factors as identified by NICE (see 18 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index Tables 2 and 3 in the Appendix), and “otherwise healthy” RECOMMENDATION participants were isolated for sensitivity analysis. The 15. BMI  ≥ 30 kg/m2 alone is not an indicator for results determined that otherwise healthy nulliparous hospital birth. Midwives should support choice of and multiparous participants with a BMI of 35.1-40 kg/ birthplace for clients with a BMI ≥ 30 kg/m2. [II- m2 were not at a significantly greater risk of adverse 2-B] [new 2019] maternal outcomes that would require obstetric care – although the researchers did indicate that their sample size might have been too small to detect a difference LOW-BMI PREGNANCY between the groups. Participants with a BMI of 35.1-40 kg/m2 were also not at a significantly greater risk for Background adverse neonatal outcomes (including Apgar < 7 at five In 2008, Statistics Canada estimated the prevalence of minutes and neonatal unit admission); and there were BMI < 18.5 kg/m2 as 2% for individuals aged 18 years no significant differences between these groups for other and older. (108) While many studies examine the health outcomes examined, including transfer to obstetric impacts of obesity, fewer studies have examined the health care, shoulder dystocia, general anesthesia, vaginal consequences of those who are underweight, with the birth, perineal trauma and maternal blood transfusion. exception of those that examine the health of individuals Furthermore, 88.3% of those with a BMI of 35.1-40 kg/ with eating disorders such as anorexia nervosa and m2 had an uncomplicated vaginal birth without third- or bulimia. In general, depending on the BMI categorization fourth-degree perineal trauma, instrumental assistance used to define underweight and the contributing factors or blood transfusion, which is comparable to the that lead to being underweight (e.g., disease, malnutrition, proportion of recommended-BMI participants in this genetically lean body type), expert opinion varies on the sample with similar birth experiences (82.7%). However, actual health consequences of low BMI. In Canada, the those with a BMI of 35.1-40 kg/m2 had a slightly greater health of underweight individuals has not been found risk of caesarean section (AdjRR 1.62, 95% CI 1.02-2.57), to differ substantially from the reference group (BMI and the risk for an urgent caesarean section was higher 18.5-24.9 kg/m2). (109) This may be particularly true for for nulliparous participants specifically (AdjRR 1.80, individuals who are well nourished but maintain a low 95% CI 1.05-3.08). Nulliparous participants with a BMI BMI due to a genetically lean body type. These clients of 35.1-40 kg/m2 also had a significantly higher risk for will not likely require specialized care that differs from postpartum hemorrhage (AdjRR 3.01, 95% CI 1.24-7.31). that received by clients within the recommended BMI These findings highlight the importance of parity in range, especially if they have no other risk factors during evaluating the risks for pregnancy complications among pregnancy. However, when malnutrition or disordered those with a BMI of 35.1-40 kg/m2. (106) eating are the cause of low BMI, maternal morbidity and mortality may result from micronutrient deficiency, Taken together, this evidence suggests that high BMI infections and anemia. (110,111) on its own is not an indication for hospital birth, and that adverse intrapartum and neonatal risks are low Associated Complications for otherwise healthy pregnant people with high BMI, Low BMI is associated with decreased rates of preeclampsia, particularly for those who have given birth before. gestational hypertension, induction of labour, caesarean Midwives should support normal birth and choice of delivery and fetal macrosomia when compared with birthplace for pregnant individuals with high BMI while other BMI categories. (112,113) Moreover, pregnant taking into account the client’s full clinical picture, individuals with low BMI exhibit similar rates of chest/ values and preferences. Informed choice discussions breastfeeding initiation and exclusive chest/breastfeeding with clients should not only address the potential risks (114), stillbirth (80), preterm birth < 32 weeks (115) and for intrapartum complications, but should also include congenital heart defects (81,116) as pregnant people within information on the potential benefits of giving birth at the recommended BMI (see Table 6). However, individuals home or in a birth centre, such as greater comfort and with low BMI at the point of conception have been shown reduced risks for medical intervention. (107) to be at an increased risk for the complications listed under Mild Risk Factors in Table 6. Similar to Tables 4 (a, b and 19 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index c) and 5 (a, b and c), Table 6 includes the available risk (Complications of High BMI), and it should be interpreted information from current meta-analyses and systematic with caution. In particular with low-BMI, research in this reviews published in 2010-2018. This research is also area is also limited by a failure to determine how the factors subject to the same limitations mentioned previously that have contributed to low-BMI (e.g., nutrition, poverty, in the risk factor section for high-BMI pregnancies genetics) may influence health outcomes. Table 6: Risk factors for low BMI < 18.5 kg/m2 compared with recommended BMI 18.5-24.9 kg/m2 Complication(s) OR/RR/OR range Negligible risk factors* Congenital heart defects 0.99-1.02 (81,116) Stillbirth 1.11** (80) Preterm birth < 32 weeks 1.13*** (115) Mild risk factors Miscarriage 1.08 (33) Preterm birth 1.25 (115) 32-36 weeks Preterm birth 1.29-1.32 (80,115,117) < 37 weeks Low birth weight 1.47-1.64 (86,115) (< 2500 g) Intrauterine growth restriction 1.54 (115) Low birth weight 1.67 (80) (< 2000 g) Small for gestational age 1.64-1.81 (80,86,117) *The statistical analysis determined that the risk for these outcomes did not significantly differ from the recommended BMI comparison group; thus risk is considered negligible. **Non-significant confidence interval: 95% CI (0.96-1.29) ***Non-significant confidence interval: 95% CI (0.92-1.38) Malnutrition and Other Comorbidities significant risk for morbidities, including seizures, Nutrition before conception and during pregnancy respiratory distress and hyperbilirubinemia. (87) Long- plays a vital role in the health of a growing fetus. (118) term outcomes for infants below the third percentile Individuals with low BMI are more likely to suffer from include metabolic disorders in adulthood, insulin poor nutritional status or malnourishment, which if left resistance and type 2 diabetes, hypertension, obesity unaddressed can have important health consequences and cardiovascular disease. (87,120) In an effort to for the pregnant parent and the infant. The association prevent morbidity and ensure optimal fetal growth in between low BMI and low birth weight (LBW), SGA, utero, midwives may support low-BMI clients who wish preterm birth and intrauterine growth restriction to learn more about their nutritional needs through (IUGR) are thought to be linked to a lack of nutrients education and/or by referring clients to a nutritionist if delivered from pregnant parent to developing fetus, necessary or when requested. Underweight clients may thereby stunting fetal growth. (115,118,119) Infants also be closely monitored for appropriate fetal growth with a birth weight at or below the third percentile throughout pregnancy via ultrasound or serial growth (equivalent to two standard deviations below the studies as needed. mean birth weight for their gestational age) are at 20 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index Aside from malnutrition, the presence of disordered BMI on its own, without complications, is not cause eating and/or over-exercising behaviours, drug use or to automatically categorize a client as high risk. When underlying medical conditions may be common among careful assessment of term-underweight pregnant people low-BMI individuals in developed countries. (115) rules out SGA, IUGR and LBW infants, there is no Although the independent impact of low BMI on the risk increased risk compared with the risk for those within of health complications is rather mild (as can be seen the recommended BMI. Likewise, among pregnant in Table 6), the presence of other comorbid conditions people who have a high BMI but do not exhibit any of such as anorexia or prolonged nicotine use severely the comorbidities discussed, and in whom the index increases the risks for serious health consequences such of suspicion for an LGA or macrosomic infant is low, as intrauterine growth restriction. (121) complications such as postpartum hemorrhage and caesarean section may not prove problematic. RECOMMENDATION Midwives should take particular care in discussions with 16. Clients  with a BMI < 18.5 kg/m2 are at higher risk high-BMI clients, as qualitative research demonstrates of IUGR, SGA and LBW. If poor fetal growth is that these individuals often experience labelling, suspected, offer third-trimester ultrasound or serial stereotyping and discrimination from health care growth studies as necessary to rule out IUGR. [II- professionals during their pregnancies. Participants in 2-B] this research have reported that health care providers often avoid discussions about obesity, make assumptions Fertility about the participants’ lack of physical ability, and focus Low BMI can contribute to menstrual irregularities and specifically on the health of the fetus, disregarding the infertility problems, which may increase the difficulty pregnant parent’s feelings or experience. These findings of calculating an estimated due date by menstrual emphasize how the perception of high-BMI clients as history alone, compared with people who have regular high risk for medical intervention is disempowering, and cycles. (122) Individuals with low BMI are also at a may result in poor care, over-treatment or over-diagnosis slightly increased risk for miscarriage compared with within this population. (123) recommended-BMI individuals (RR 1.08 95% CI 1.05- 1.11, p < 0.0001). (33) Although discussion about BMI can be challenging, midwives can still provide thoughtful support and positive reinforcement throughout pregnancy and RECOMMENDATION postpartum for clients with high or low BMI. When 17. M  idwives should perform a thorough menstrual appropriate, comments regarding weight should involve history with every client. For those who report the sensitive use of language and should be clear and menstrual irregularities, discuss the risks and carefully explained within the context of the client’s benefits of a dating ultrasound, preferably prior to unique clinical picture. 14 weeks’ gestation. [I-A] Each client deserves to be given an individualized care CONCLUSION plan, which may or may not include issues related to BMI. An appropriate approach is to offer a realistic This clinical practice guideline highlights some of the discussion about the risks associated with high or low health complications that individuals with high or low BMI, the significance of complications should they BMI may face during and after pregnancy. It is important develop, and an assessment of the midwife’s ability to to note that not all individuals within a particular BMI respond to them. category have an equal likelihood of experiencing complications. The possible consequences of labelling individuals high risk before any complications actually occur also need to be taken into account. High or low 21 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index SUMMARY OF RECOMMENDATIONS 1. Offer  referral to the most appropriate and available mental health services for clients who have or are suspected of having an eating disorder. [III-C]  2. Discuss the benefits of optimizing GWG in pregnancy for clients with a BMI < 18.5 kg/m2 or ≥ 30 kg/m2. [II-2-B] [new 2019] 3. Midwives  may consider calculating and documenting pre-pregnancy BMI on the first antenatal record. If pre-pregnancy weight is unknown, midwives may consider documenting BMI at the intake visit. [III-B] [new 2019] 4. All  clients should be counselled about the importance of good nutrition and physical activity during pregnancy. Canada’s Food Guide is an example of a nutrition guideline that includes dietary advice for individuals who are pregnant or nursing. [II-2-B] 5. For  clients with a BMI < 18.5 kg/m2 or ≥ 30 kg/m2, midwives should identify and offer referrals to the most appropriate health care providers available in clients’ communities to discuss nutrition, healthy eating and other good habits. [II-2-B] High BMI 6. O  btain and document a baseline blood pressure, using the appropriate cuff size for clients with a BMI ≥ 30 kg/m2. [II-2-B] 7. For clients with a BMI ≥ 30 kg/m2, midwives should discuss the higher risk of preeclampsia and GDM, along with the risks and benefits of GDM screening. [II-2-A] [new 2019] 8. Midwives should individually evaluate each client’s need for thromboprophylaxis. They may consider offering an antepartum consultation with a physician for clients with a BMI ≥ 40 kg/m2, or for clients with a BMI ≥ 30 kg/m2 and other known risk factors for thromboembolism. [III-C] [new 2019] 9. For  second-trimester ultrasounds reporting suboptimal visualization, discuss limitations of ultrasound with client and consider offering repeat ultrasound if needed. [III-B] 10. When  abdominal palpation proves challenging and/or symphysis-fundal measurements are unreliable, midwives should discuss risks and benefits of a third-trimester ultrasound and offer as necessary to address any information gaps. [II-2-B] 11. Midwives  should consider offering an antepartum anesthesiology consultation for clients who plan an epidural, or for those who wish to have a more detailed discussion about potential anesthesia complications related to BMI ≥ 30 kg/m2. [III-C] 12. Midwives are well suited to help clients with a BMI ≥ 30 kg/m2 who may experience difficulties with nursing to establish good positioning, latch and milk supply. When appropriate, midwives should refer clients to a lactation consultant or other specialist for lactation support. [III-B] 22 AOM Clinical Practice Guideline 12 | The Management of High or Low Body Mass Index 13. For  clients with a BMI ≥ 30 kg/m2, midwives should discuss the benefits of a diet high in nutrient-dense, folate-containing foods before and during pregnancy to reduce the risk of NTDs. For clients who cannot maintain a high-folate diet, midwives may also discuss the risks and benefits of administering a supplement with 0.4 mg to 5 mg of folic acid. [II-2-B] [new 2019] 14. Midwives should ensure that they feel competent to perform venipuncture and gain IV access in clients with a BMI ≥ 30 kg/ m2, and may consider establishing IV access during labour in clients who choose home birth. [III-C] 15. BMI  ≥ 30 kg/m2 alone is not an indicator for hospital birth. Midwives should support choice of birthplace for clients with a BMI ≥ 30 kg/m2. [II-2-B] [new 2019] Low BMI 16. Clients  with a BMI < 18.5 kg/m2 are at higher risk of IUGR, SGA and LBW. If poor fetal growth is suspected, offer third- trimester ultrasound or serial growth studies as necessary to rule out IUGR. [II-2-B] 17. 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