Hypertensive Disorders of Pregnancy

• Clinical Practice Guideline 15 addresses hypertensive disorders of pregnancy (HDP).
• The guideline is for Ontario midwives for management of HDP.
• The guideline was updated in 2022-2023 to include literature published from 2012 to 2021.
• An updated guideline version was approved March 28, 2023.

Authors and Contributors

• Claire Carnegie, Tasha MacDonald, and Alexa Minichiello are the authors (2023).
• The Clinical Practice Guideline Committee contributed in 2023, chaired by Anna Meuser.
• AOM staff Pamela Vazac and Faduma Gure contributed.
• The Quality, Insurance and Risk Management Committee contributed with Bounmy Inthavong, Lucia D'Amore, and Barbara Borland.
• Contributors from 2012 are also listed, including the HDP CPG Working Group.

Acknowledgements

• The Association of Ontario Midwives (AOM) acknowledges financial support from the Ministry of Health.
• This guideline is aligned with the AOM's commitment to Gender Inclusivity and Human Rights, reflecting trans, genderqueer, and intersex communities.
• The guideline has been reviewed using a modified AGREE instrument (Appraisal of Guidelines for Research and Evaluation).

Abbreviations

• Key abbreviations used in the guideline include AOR (Adjusted odds ratio), ACR (Albumin:creatinine ratio), ALT (Alanine aminotransferase), AST (Aspartate aminotransferase), BMI (Body mass index), BP (Blood pressure), dBP (Diastolic blood pressure), sBP (Systolic blood pressure), CI (Confidence interval), CS (Cesarean section), HELLP (Hemolysis, elevated liver enzymes, low platelet count), HDP (Hypertensive disorders of pregnancy), IUGR (Intrauterine growth restriction), NST (Non-stress test), OR (Odds ratio), PAPP-A (Pregnancy-associated plasma protein A), PCR (Protein:creatinine ratio), PROM (Prelabor rupture of membranes), RCT (Randomized controlled trial), RR (Relative risk), and SGA (Small for gestational age).

Aim and Objectives

• The guideline aims to offer evidence-based information for antepartum, intrapartum, and postpartum management of hypertensive disorders in pregnancy (HDP), consistent with midwifery philosophy and model of care.
• Objectives include reviewing research on screening, diagnosis, and management of HDP within Ontario midwifery care, covering definitions, incidence, risk factors, prevention, screening, management, and client experiences.

Outcomes of Interest

• Critical patient outcomes include incidence of HDPs, morbidity*, mortality, rates of induction, and cesarean section.
• Neonatal outcomes include neonatal mortality, neonatal morbidity, and preterm birth.

Literature Search and Methods

• MEDLINE, CINAHL, and Cochrane Library searches from 2009-2021 were used.
• The GRADE methodology is used to determine certainty of evidence and strength of recommendations, considering risk of bias, inconsistency, indirectness, imprecision, and publication bias.

Certainty of Evidence and Types of Statements

• Evidence certainty is categorized as High, Moderate, Low, or Very Low, influencing decision-making.
• Recommendations are strong ("should") or weak ("may"), reflecting the degree of confidence that benefits outweigh harms.
• Types of statements include Recommendations, No recommendation, Good practice statements, and Summary statements.

Strength of Recommendation

• Strong recommendations indicate that benefits clearly outweigh risks and burdens.
• Weak recommendations suggest that benefits, risks and burdens are closely balanced.
• The labels of [New 2023] and [2023] are used to mark changes to recent recommendations.

Introduction to HDP

• Hypertensive disorders of pregnancy (HDP) include pre-existing hypertension, gestational hypertension, and preeclampsia.
• HDPs are a major cause of poor pregnancy outcomes in Canada and internationally.
• Midwives monitor for elevated blood pressure and other signs and symptoms of HDP given elements of care may fall outside legislative scope of practice.

Definitions

• Hypertension in pregnancy: Clinic systolic BP ≥ 140 mmHg and/or diastolic BP ≥ 90 mmHg (average of two readings after 5 minutes' rest, 15 minutes apart).
• Severe hypertension: sBP ≥ 160 mmHg and/or dBP ≥ 110 mmHg (average of two readings within 15 minutes).
• Transient hypertension: Elevated BP ≥ 140/90 mmHg in a clinic setting, resolving with repeated BP measurement.
• White-coat hypertension: Clinic BP ≥ 140/90 mmHg, out-of-office BP < 135/85 mmHg.
• Masked hypertension: Clinic BP < 140/90 mmHg, out-of-clinic BP ≥ 135/85 mmHg.
• Proteinuria: ≥ 30 mg/mmol urinary PCR, or ACR ≥ 8 mg/mmol or ≥ 0.3 g/day in 24-hour urine.

Diagnoses and Classification

• HDPs are classified as chronic (pre-existing) hypertension or gestational hypertension (onset at ≥ 20 weeks).
• Preeclampsia: Gestational hypertension with new-onset proteinuria, or one or more adverse conditions.

Incidence of HDP

• Approximately 7% of pregnancies in Canada are affected by hypertensive disorders.
• Ontario midwifery clients (April 1, 2020 – March 31, 2021): 0.3% had pre-existing hypertension, 2.9% gestational hypertension, 0.7% preeclampsia.
• Hypertensive was associated with 1.2 deaths per 100 000 hospital deliveries in Canada (2003-2004, 2014-2015).

Physiology of Hypertensive Disorders in Pregnancy

• In HDPs, normal physiological processes to meet increased metabolic demands and blood flow are impaired.
• Preeclampsia is divided into early (placental origin, < 34 weeks) and late onset (oxidative changes, genetic susceptibility, ≥ 34 weeks).

Pathophysiology of Preeclampsia

• Incomplete trophoblast remodeling of spiral arteries leads to reduced placental perfusion.
• Oxidative stress triggers syncytiotrophoblasts to release pro-inflammatory cytokines, exosomes, anti-angiogenic agents and cell-free fetal DNA.
• This provokes systemic inflammation.

Systemic Manifestations

• Vasospasm and increased blood pressure, abnormal coagulation and thrombosis, and increased endothelial permeability.
• Poor placentation can cause fetal growth restriction and stillbirth or neonatal death.

Associated Complications

• Preeclampsia outcomes depend on onset age and severity. HDP increases risk of placental abruption, organ failure, cerebrovascular accident and DIC, IUGR, intrauterine death.
• Hemolysis, elevated liver enzymes, and low platelets syndrome (HELLP) can occur.
• Outcomes are disproportionately greater in Black patients
• Strategies to eliminate racism should be undertaken and promoted.

Risk Factors for HDP

• Many risk factors include: obesity, nulliparity, prior preeclampsia, diabetes, multiple pregnancy.

Risk Factors for Preeclampsia

• Prior pregnancy with preeclampsia (RR 8.4, 95% CI 7.1 to 9.9)
• Chronic hypertension (RR 5.1)
• Pregestational diabetes (RR 3.7)
• Multifetal pregnancy and BMI > 30 (RR 2.9 and 2.8 respectively). Other Risk Factors are summarized with RR values.
• Midwives should ID Risk Factors early in care. [2023]

Prediction of HDP

• Risk stratification systems are integrated for use in routine antenatal care (SOGC, NICE). Pregnant people are high risk if they have one or more high risk factors or two or more moderate risk factors.
• Low serum levels of pregnancy-associated plasma protein A (PAPP-A) are known to be associated with preeclampsia.

First Trimester Prediction

• A 2017 meta-analysis of eight studies with a total of 132,000 participants (moderate certainty of evidence) shows those with low PAPP-A (< 5th centile) in the first trimester are two times more likely to develop preeclampsia than those with PAPP-A (> 5th centile) (OR 1.94, 95% CI 1.63-2.30). (64)
• Current recommendations note to review client clinical history to ID risk factors for early preeclampsia.

Second Trimester Prediction

• Measurement of PIGF is a better predictor of preeclampsia when taken after the first trimester of pregnancy.

Multiple marker algorithms

• The Fetal Medicine Foundation (FMF) combines data from clinical risk factors and measurements from uterine artery pulsatility index (UtA-PI), mean arterial pressure (MAP), and placental growth factor (PIGF): demonstrated better effectiveness.
• Algorithm includes race as an input, which may result in additional interventions and unwarrented management.
• Midwives determine individuals level of preeclampsia risk and preventive measures. [2023]

Prevention of HDP

• 50-150 mg reduces the risk of preeclampsia, with the greatest risk reduction when at high risk, ≥75 mg, initiated ≤ 16 weeks' gestation (RR 0.89, 95% CI 0.82-0.95). (79)
• Low-dose ASA can be daily dose 165 mg or greater

Vitamin D

• Vitamin D supplementation (7,8). Recommendation 4: Midwives may offer calcium supplementation (1000-2500 mg/day). Calcium supplementation has not historically is low but there may be two more cases of HELLP syndrome.

Vitamin C+E

• Vitamin C/E supplementation not recommended for the prevention. [new 2023]
• Folic acid + multivitamins has established benefits and multivitamin with folic may the risk of.

Vitamin D, Selenium and L-arginine

• Insufficient evidence to support for the prevention of 7).
• A 2015 Cochrane review show vitamin results little to no difference the 48. However, the studies used varying ranging from to IU, which.

Uncertain and Conflicting Evidence

• Conflicting evidence regarding is required but a 2021 95% CI -. may HDP.
• Supplements and there is one in increase. Preventive Benefit HDP.

Antenatal Considerations for HDP Screening

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