Chapter 10 Assessment of High-Risk Pregnancy PDF

lOMoARcPSD|15450111 Chapter 10 Assessment of High-Risk Pregnancy Maternal Health (Samuel Merritt University) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Chapter 10 Assessment of High-Ris...

lOMoARcPSD|15450111 Chapter 10 Assessment of High-Risk Pregnancy Maternal Health (Samuel Merritt University) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Chapter 10 Assessment of High-Risk Pregnancy Assessment of Risk Factors Biophysical Factors originate within the mother or fetus and affect the development or functioning of either one or both (genetic disorders, problems related to nutritional and general health status, and medical or obstetric-related illnesses) Genetic Considerations Genetic factors may interfere with normal fetal or neonatal development, result in congenital anomalies, or create difficulties for the mother. These factors include defective genes, transmissible inherited disorders and chromosomal anomalies, multiple gestations, large fetal size, and ABO incompatibility Nutritional Status Adequate nutrition, without which fetal growth and development cannot proceed normally, is one of the most important determinants of pregnancy outcome. Conditions that influence nutritional status include the following: young age, three pregnancies in the previous 2 years, tobacco alcohol or drug use, inadequate dietary intake because of chronic illness or food fads, inadequate or excessive weight gain, hematocrit value less than 33% Medical and Obstetric Disorders Complications of current and past pregnancies, obstetric-related illnesses, and pregnancy losses put the woman at risk Psychosocial Factors maternal behaviors/adverse lifestyles that have a negative effect on the health of the mother or fetus (emotional distress, history of depression/mental health, disturbed interpersonal relationships: intimate partner violence, substance use/abuse, inadequate social support, unsafe cultural practices) Smoking A strong, consistent, causal relation has been established between maternal smoking and reduced birth weight. Risks include: LBW infants, higher neonatal mortality rates, increased rates of miscarriage, increased incidence of premature rupture of membranes. These risks are aggravated by low socioeconomic status, poor nutritional status, and concurrent use of alcohol Caffeine Birth defects in humans have not been related to caffeine consumption. However, pregnant women who consume more than 200mg of caffeine daily (~12oz of coffee per day) may be at increased risk for giving birth to infants with intrauterine growth restriction (IUGR) Alcohol Although the exact effects of alcohol in pregnancy have not been quantified and its mode of action is largely unexplained, it exerts adverse effects on the fetus, resulting in fetal alcohol syndrome, fetal alcohol effects, learning disabilities, and hyperactivity Drugs The developing fetus may be affected adversely by drugs through several mechanisms. They can be teratogenic, cause metabolic disturbances, produce chemical effects, or cause depression or alteration of central nervous system function. This category includes medications prescribed by PCP or OTC and commonly abused drugs such as heroin, cocaine, and marijuana. Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Psychologic Status Childbearing triggers profound and complex physiologic, psychologic, and social changes, with evidence to suggest a relationship between emotional distress and birth complications. This risk factor includes conditions such as specific intrapsychic disturbances and addictive lifestyles, history of child abuse or intimate partner violence, inadequate support systems, family disruption or dissolution, maternal role changes or conflicts, noncompliance with cultural norms, unsafe cultural, ethnic or religious practices, and situational crises Sociodemographic Factors arise from the mother and her family. These risks may place the mother and fetus at risk. Examples: lack of prenatal care, low income, single marital status, and being a member of a minority ethnic group Low income Poverty underlies many other risk factors and leads to inadequate financial resources for food and prenatal care, poor general health, increased risk for medical complications of pregnancy, and greater prevalence of adverse environmental influences Lack of Prenatal Care Failure to diagnose and treat complications early is a major risk factor arising from financial barriers or lack of access to care; depersonalization of the system resulting in long waits, routine visits, variability in health care personnel, and unpleasant physical surroundings, lack of understanding of the need for early and continued care or cultural beliefs that do not support the need, and fear of the health care system and its providers Age Women at both ends of childbearing age spectrum have an increased incidence of poor outcomes; however, age not risk factor in all cases. Physiologic and psychologic risks should be evaluated Adolescents Possible pregnancy and birth complications include anemia, preeclampsia, prolonged labor, and contracted pelvis and cephalopelvic disproportion. Long-term social implications of early motherhood are lower educational attainment, lower income, increased dependence on government support programs, higher divorce rates, and higher parity Mature Mothers Risks to older mothers not just age but other considerations: number and spacing of previous pregnancies, genetic disposition of parents, medical history, lifestyle, nutrition, prenatal care. Increased chronic disease and complications that arise from invasive medical management of pregnancy and labor with demographic characteristics put older women at risk. Conditions more likely to be experienced by mature women: chronic HTN and preeclampsia, diabetes, prolonged labor, c-section, placenta previa, placental abruption, and death. Fetus at greater risk for LBW and macrosomia, chromosomal abnormalities, congenital malformations, neonatal death Parity Number of previous pregnancies is a risk factor associated with age and includes all first pregnancies, especially a first pregnancy at either end of the childbearing age continuum. The incidence of preeclampsia and dystocia is increased with a first birth Marital Status The increased mortality and morbidity rates for unmarried women, including an increased risk for preeclampsia, are often related to inadequate prenatal care and a young childbearing age Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Residence The availability and quality of prenatal care vary widely with geographic residence. Women in metropolitan areas have more prenatal visits than those in rural areas have fewer opportunities for specialized care and consequently a higher incidence of maternal mortality. Health care in the inner city, where residents are usually poorer and begin childbearing earlier and continue longer, may be of lower quality than in a more affluent neighborhood Ethnicity Although ethnicity itself is not a major risk, race is associated with some poor pregnancy outcomes. In the United States, ex. African-American women have the highest rates of preterm birth, almost twice as high as those of other racial and ethnic groups Environmental Factors Various environmental substances can affect fertility and fetal development, the chance of live birth, and the child’s subsequent mental and physical development. Environmental influences include infections, radiation, chemicals such as mercury and lead, therapeutic drugs, illicit drugs, industrial pollutants, cigarette smoke, stress, and diet. Paternal exposure to mutagenic agents in the workplace has been associated with an increased risk of miscarriage Environmental factors include hazards in the workplace and the woman’s general environment and may include environmental chemicals (lead, mercury), anesthetic gasses, and radiation Specific Pregnancy Problems and Related Risk Factors: Polyhydramnios Poorly controlled diabetes, fetomaternal hemorrhage, fetal congenital anomalies (GI obstruction, CNS abnormalities), genetic disorders, twin-twin transfusion syndrome Intrauterine Growth Restriction Maternal Causes Hypertensive disorders, pregestational diabetes, cyanotic heart disease, autoimmune disease, restrictive pulmonary disease, multifetal gestation, malabsorptive disease/malnutrition, living at a higher altitude, tobacco/substance abuse Fetal Causes Genetic disorders, teratogenic exposure, fetal infection Oligohydramnios Renal agenesis (Potter syndrome), premature rupture of membranes, prolonged pregnancy, uteroplacental insufficiency, severe intrauterine growth restriction (IUGR), maternal hypertensive disorders, maternal dehydration/hypovolemia Chromosomal Abnormalities Advanced maternal age, parental chromosomal rearrangements, previous pregnancy with autosomal trisomy, abnormal ultrasound findings during current pregnancy (fetal structural anomalies, IUGR, amniotic fluid volume abnormalities), increased risk as calculated from noninvasive screening results (nuchal translucency and maternal serum analytes) Antepartum Testing Goals: identify fetuses at risk for injury due to interrupted oxygenation so permanent injury or death may be prevented AND identify appropriate oxygenated fetuses so unnecessary interventions can be avoided Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Monitoring begins by 32-34 weeks of gestation and continues regularly until birth Common Maternal and Fetal Indications for Antepartum Testing: Diabetes, chronic HTN, preeclampsia (with or without severe features), suspected or confirmed fetal growth restriction, multiple gestation, oligohydramnios, preterm premature rupture of membranes, late-term or postterm gestation, previous stillbirth, decreased fetal movement, systemic lupus erythematosus, renal disease, cholestasis of pregnancy Biophysical Assessment Daily Fetal Movement Count Assessment of fetal activity → “kick count”, can be assessed at home, noninvasive, inexpensive, simple One recommendation - count once a day for 60 minutes or count 2-3 times daily (after meals or before bedtime) or until 10 movements are counted or count all fetal movements in 12-hour periods each day Fetal alarm signal – fetal movement ceases entirely for 12 hours A count fewer than 3 fetal movements within 1 hour warrants further evaluation by nonstress test or contraction stress test and a complete/modified biophysical profile In assessing fetal movement, not present during fetal sleep cycle, reduced temporarily if woman taking depressant medications, drinking alcohol, or smoking cigarette, do not decrease as woman nears term, obesity decreases perception of fetal movements and ability for mother to count them Ultrasonography Info about fetal activity and gestational age, normal vs abnormal fetal growth curves, fetal and placental anatomy, fetal well-being, visual assistance with which invasive tests can be performed more safely Sound is a form of wave energy that causes small particles in a medium to oscillate Hertz – frequency of sound refers to the number of peaks or waves that move over a given point per unit of time When directional beams of sound strike an object, an echo is returned Time delay between the emission of the sound and the return and direction of the echo is noted ○ From these data, the distance and location of an object can be calculated Ultrasound is sound frequency higher than that detectable by humans (>20000hz) Ultrasound images are a reflection of the strength of sending beam, the strength of returning echo, and the density of the medium [muscle (uterus), bone, tissue (placenta), fluid, or blood] through which the mean is sent and returned Ultrasound examination can be performed either abdominally or transvaginally during pregnancy Ultrasound scans produce 2D/3D view of the area being examined and can be used to create pictorial images Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Types of Ultrasound Scans: Two-dimensional — sound waves sent straight down from ultrasound transducer, image appears flat, black white or shades of gray, standard medical scan Three-dimensional — sound waves sent out at different angles, returning echoes are processed by computer to add depth, sepia tones rather than black and white, scan used for diagnostic or management purposes Four-dimensional — add time to 3D scan, recorded and played back in succession, continuously updated - the fetus is viewed in real-time Abdominal ultrasonography is more useful after the first trimester when the pregnant uterus becomes an abdominal organ Woman should have full bladder to displace uterus upward to provide a better image of the fetus Transmission gel/paste applied to enhance transmission and reception of the sound waves before transducer is moved over the skin Transvaginal ultrasonography (probe inserted into vagina) allows pelvic anatomic features to be evaluated in greater detail and intrauterine pregnancy to be diagnosed earlier Does not require full bladder, useful for obese woman with thick abdominal layers Used in first trimester to detect ectopic pregnancies, monitor developing embryo, help identify abnormalities, help establish gestational age May be used along with abdominal scanning to evaluate preterm labor in 2-3 trimester pregnancy Levels of Ultrasonography 1. Standard (basic) used to evaluate fetal presentation, amniotic fluid volume (AFV), cardiac activity, placental position, fetal growth parameters, number of fetuses, anatomic survey of fetus 2. Limited performed to determine specific piece of information about pregnancy - identify fetal presentation during labor or estimating AFV 3. Specialized (detailed) or targeted performed if woman is suspected of carrying an anatomically or physiologically abnormal fetus - indications: abnormal history or laboratory findings or results of previous standard or limited ultrasound examination Indications for Use During first trimester: number, size, location of gestational sacs, presence/absence of fetal cardiac and body movement, presence/absence of uterine abnormalities (bicornuate uterus or fibroids) or adnexal masses (ovarian cysts or ectopic pregnancy), pregnancy dating During second and third: assess fetal viability, number, position, gestational age, growth pattern and anomalies, amniotic fluid volume, placental location and condition, presence of uterine fibroids or anomalies, presence of adnexal masses, cervical length Ultrasonography provides early diagnoses, allowing therapy to be instituted earlier thereby decreasing severity and duration or morbidity (physical and emotional) for the family Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Major Uses of Ultrasonography During Pregnancy First Trimester Second Trimester Confirm pregnancy Confirm viability Determine gestational age Rule out ectopic pregnancy Detect multiple gestations Determine cause of vaginal bleeding Visualization during chorionic villus sampling Detect maternal abnormalities such as bicornuate uterus, ovarian cysts, fibroids Fetal Heart Activity Establish or confirm dates Confirm viability Detect polyhydramnios, oligohydramnios Detect congenital anomalies Detect IUGR Assess placental location Visualization during amniocentesis Evaluate for preterm labor Third Trimester Confirm gestational age Confirm viability Detect macrosomia Detect congenital anomalies Detect IUGR Determine fetal position Detect placenta previa or placental abruption Visualization during amniocentesis, external version Biophysical profile Amniotic fluid volume assessment Doppler flow studies Detect placental maturity Evaluate for preterm labor Can be demonstrated by about 6 weeks of gestation using transvaginal ultrasound When fetus in favorable position, fetal cardiac anatomy using transvaginal ultrasound is possible in most patients at 13 weeks of gestation Fetal death can be confirmed by lack of heart motion along with presence of fetal scalp edema and maceration and overlap of the cranial bones Gestational Age Gestational dating by ultrasonography is indicated for conditions such as uncertainty of date of last normal period, recent discontinuation of oral contraceptives, bleeding episode during 1st trimester, uterine size that does not match dates, other high-risk condition Done best with ultrasound measurements, ignoring menstrual dates Ultrasound measurements: crown-rump length in the first trimester and biparietal diameter (BDP), head circumference, abdominal circumference, femur length after the first trimester Fetal Growth Determined by both intrinsic growth potential and environmental factors Conditions that require ultrasound assessment of fetal growth include poor maternal weight gain or pattern of weight gain, previous pregnancy with IUGR, chronic infections, ingestion of drugs (tobacco, alcohol, OTC and street drugs), maternal diabetes, hypertension, multifetal pregnancy, other medical or surgical complications Serial evaluation of BPD, limb length, and abdominal circumference can allow differentiation among size discrepancies resulting from inaccurate dates, true IUGR, and macrosomia IUGR may be symmetric (fetus is small in all parameters) or asymmetric (head and body growth do not match) Symmetric: reflects chronic or long-standing insult and may be caused by low genetic growth potential, intrauterine infection, chromosomal anomaly, maternal undernutrition, heavy smoking Asymmetric: acute or late-occurring deprivation such as placental insufficiency resulting from hypertension, renal disease, or cardiovascular disease Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Reduced fetal growth - one of the most frequent conditions associated with stillbirth Macrosomic infant - increased risk for traumatic injury and asphyxia during birth (sym or asym) Fetal Anatomy Anatomic structures that can be identified by ultrasonography (depending on gestational age): Head (including ventricles and blood vessels), neck, spine, heart, stomach, small bowel, liver, kidneys, bladder and limbs Ultrasonography permits confirmation of normal anatomy and detection of major fetal malformations Fetal Genetic Disorders and Physical Anomalies Prenatal screening technique called nuchal translucency (NT) screening uses ultrasound measurement of fluid in the nape of the fetal neck between 10-14 weeks gestation to identify possible fetal abnormalities When combined with abnormal maternal serum marker levels, elevated NT indicates possible increased risk for certain chromosomal abnormalities in the fetus (trisomies 13, 18, 21) An elevated NT alone indicates an increased risk for congenital heart defects Other ultrasound findings that predict trisomy 21 are an absent nasal bone, shortened femur or humerus, echogenic intracardiac focus, echogenic bowel, pyelectasis (enlargement of renal pelvis, part of kidney that collects urine), and an abnormally fast or slow fetal heart rate Findings considered soft markers only, not diagnostic for chromosomal anomaly Placental Position and Appearance Ability to diagnose serious problems related to placental location in a timely manner Between 18-23 weeks gestation, edge of placenta extends to or covers internal os of the cervix However, most cases of placenta previa diagnosed during the second trimester resolve by term because elongation of lower uterine segment as pregnancy advances So if placenta previa diagnosed during second placenta, need repeated ultrasounds because placenta moves away from cervical os Placental appearance – many changes observed in placenta are related to calcification, fibrosis, infarction “Globular” placenta with a narrow base in comparison to height is associated with an increased rate of IUGR, fetal death, and other complications Adjunct to Other Invasive Tests Safety of amniocentesis is increased when position of fetus, placenta, umbilical cord, pockets of amniotic fluid can be identified accurately – reduced risk of fetomaternal hemorrhage from pierced placenta Percutaneous umbilical blood sampling and chorionic villus sampling are guided by ultrasonography to identify cord and chorion frondosum accurately Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Fetal Well-Being Physiologic parameters of the fetus that can be assessed with ultrasound scanning: AFV, vascular waveforms from fetal circulation, heart motion, fetal breathing movements (FBMs), fetal urine production, fetal limb, head movements Doppler Blood Flow Analysis Uses systolic/diastolic flow ratios and resistance indice to estimate blood flow in various arteries Provides indication of fetal adaptation and reserve Vessels most often studied: fetal umbilical, middle cerebral arteries and maternal uterine arteries ○ Several restriction of umbilical artery blood flow as indicated by absent or reversed flow during diastole has been associated with IUGR Doppler ultrasound has demonstrated to be of value in reducing perinatal mortality and unnecessary obstetric interventions in fetuses with IUGR Significantly increased peak systolic velocity in the middle cerebral artery has been found to predict moderate to severe fetal anemia Abnormal maternal uterine artery Doppler waveforms used to predict fetal growth restrictions Amniotic Fluid Volume Accurate measurement of amniotic fluid volume (AFV) using ultrasound is difficult and poorly predict abnormal values Differences in amount of pressure placed on ultrasound transducer can affect accuracy of measurement Great pressure on maternal abdomen yield lower measurement, less pressure higher measurement Abnormalities in AFV are frequently associated with fetal disorders Oligohydramnios (decreased fluid) — fundal height that is small for gestational age and fetus is easily palpated ○ Objective criterion of decreased AFV is met if maximum vertical pocket of the amniotic fluid is less than 1-2cm ○ Associated with congenital anomalies (renal agenesis [Potter Syndrome]) and premature rupture of membranes Polyhydramnios (increased fluid) ○ Subjective criteria: fundal height that is large for gestational age and fetus cannot easily be palpated or that is ballotable ○ Usually objectively defined as pockets of amniotic fluid measuring more than 8cm ○ Associated with gastrointestinal and central nervous system abnormalities, multiple fetuses, fetal hydrops Total AFV can be evaluated by a method in which vertical depths (cm) of largest pocket of amniotic fluid in all four quadrants surrounding maternal umbilicus are totaled, providing an amniotic fluid index (AFI) Oligohydramnios – AFI less than 5cm Polyhydramnios – AFI is 25 cm or more Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Biophysical Profile Real-time ultrasound permits detailed assessment of the physical and physiologic characteristics of the developing fetus and cataloging of normal and abnormal biophysical response to stimuli Biophysical profile (BPP) is a noninvasive dynamic assessment of a fetus that is based on acute and chronic markers of fetal disease — Considered a physical examination of the fetus (determine vital signs) Includes AFV, FBMs, fetal movement, fetal tone determined by ultrasound and FHR reactivity determined by means of nonstress test FHR reactivity, FBMs, fetal movement and fetal tone reflect current central nervous system (CNS) status, whereas AFV demonstrates the adequacy of placental function over a longer period of time BPP is used frequently in late second or third trimester for antepartum fetal testing because it is a reliable predictor of fetal well-being — BPP of 8 or 10 with normal AFV is considered normal Advantages of test: excellent sensitivity and low false-negative rate One limitation: if fetus is in quiet sleep state, BPP can require a long period of observation unless ultrasound is videotaped, it cannot be reviewed Scoring the Biophysical Profile Biophysical Variable Score 2 At least 1 episode of fetal breathing Fetal breathing movements movements of at least 30-sec duration in a 30-min observation At least 3 trunk/limb movements in Fetal movements 30-mins At least 1 episode of active extension with return to flexion of fetal limb or Fetal tone trunk; opening and closing of hand considered normal tone Amniotic fluid index (AFI) Deepest vertical pocket >2cm Nonstress test Reactive Biophysical Profile Management Score Interpretation Normal; low risk for 10 chronic asphyxia Normal; low risk for 8 chronic asphyxia Suspect chronic asphyxia 6 4 0-2 Suspect chronic asphyxia Strongly suspect chronic asphyxia Score 0 Absent fetal breathing movements or 36 weeks Gestational age >35 weeks Open neural tube or other defect Advancing gestational age Amniocentesis Performed to obtain amniotic fluid which contains fetal cells possible after week 14 of pregnancy when uterus becomes an abdominal organ and sufficient amniotic fluid is available for testing Under direct ultrasonographic visualization, needle inserted transabdominally into uterus and amniotic fluid is withdrawn into syringe Indications: prenatal diagnosis of genetic disorders or congenital anomalies (neural tube defects [NTD]), assessment of pulmonary maturity, diagnosis of fetal hemolytic disease (rarely) Complications: Maternal – leakage of amniotic fluid, hemorrhage, fetomaternal hemorrhage with possible maternal Rh isoimmunization, infection, labor, placental abruption, inadvertent damage to intestine or bladder and amniotic fluid embolism (anaphylactoid syndrome of pregnancy) Fetal – death, hemorrhage, infection (amnionitis), and direct injury from the needle Many of complications have been minimized or eliminated by using ultrasonography to direct procedure *because of possibility of fetomaternal hemorrhage, administering Rh0D immunoglobulin to woman who is Rh negative is standard practice after an amniocentesis Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Indications for Use Genetic Concerns Increased risk for having a child with genetic disorder if: Older maternal age (35), older paternal age (40-50), parents who are affected by or are carriers of genetic disorders (sickle cell anemia, Tay-Sachs disease, cystic fibrosis), women with prior child with structural defect or with structural defect identified by ultrasound during current pregnancy, women with prior child with chromosomal abnormality Biochemical analysis of enzymes in amniotic fluid can detect inborn errors of metabolism or fetal structural anomalies Ex. alpha-fetoprotein (AFP) levels in amniotic fluid are assessed as a follow-up for elevated levels in maternal serum High AFP levels in amniotic fluid confirm diagnosis of NTD (spina bifida or anencephaly or abdominal wall defect such as omphalocele) Elevation results from increased leakage of cerebrospinal or abdominal fluid into the amniotic fluid through the closure defect Fetal Lung Maturity Late in pregnancy, accurate assessment of fetal lung maturity is possible by examining amniotic fluid to determine the lecithin/sphingomyelin [L/S] ratio or for presence of phosphatidylglycerol [PG] Require considerable time, technical expertise, cost to perform → only special cases Lamellar Body Count (LBC) has become the primary test for determining fetal lung maturity Lamellar bodies are surfactant-containing particles secreted by type II pneumocytes Number of lamellar bodies found in the amniotic fluid increases with onset of functional fetal pulmonary maturity Fetal Hemolytic Disease Before amniocentesis for identify and follow-up of fetal hemolytic disease in cases of isoimmunization Doppler velocimetry of the fetal middle cerebral artery has now replaced serial amniocentesis as the method of choice to accurately and noninvasively monitor for fetal anemia in isoimmunized pregnancies Chorionic Villus Sampling Technique for genetic studies in 1st trimester: combined advantages of earlier diagnosis and rapid results Indication similar to amniocentesis – but cannot be used for maternal serum marker screening because no fluid is obtained CVS performed in second trimester carries no greater risk for pregnancy than amniocentesis and is considered equal to amniocentesis in diagnostic accuracy When performed after the first trimester, procedure is known as “late CVS” or placental biopsy Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 CVS can be performed in the first or second trimester (ideally between 10-13 weeks gestation) and involves removal of a small tissue specimen from the fetal portion of the placenta Because chorionic villi originate in the zygote, this tissue reflects the genetic makeup of the fetus Procedure can be accomplished either transcervically or transabdominally In transcervical sampling, sterile catheter through cervical canal toward placenta under continuous ultrasonographic guidance - small portion of the chorionic villi is aspirated with a syringe In abdominal approach, 18-20 gauge spinal needle with stylet inserted under sterile conditions through abdominal wall into placenta under ultrasound guidance ○ Stylet withdrawn and chorionic tissue is aspirated in a syringe ○ This method is preferred if genital herpes, cervicitis or bicornuate uterus is present CVS is a relatively safe procedure Pregnancy loss is similar to second-trimester amniocentesis Incidence of IUGR, placental abruption, preterm birth no higher in woman with CVS than expected Because of the possibility of fetomaternal hemorrhage, women who are Rh negative should receive Rh0D immunoglobulin after CVS to prevent isoimmunization, regardless of whether procedure is performed transcervically or transabdominally unless fetus is known to be Rh negative !! Because amniocentesis and CVS are invasive tests, their use is associated with a small but concerning risk for pregnancy loss and infection !! Percutaneous Umbilical Blood Sampling Cordocentesis or funipuncture — direct access to fetal circulation during the second and third trimesters Can be used for fetal sampling and transfusion But replaced by placental biopsy because it is safer easier faster Improvements in cytogenetic and molecular diagnostic testing have decreased the need for fetal blood samples ○ Many tests that were once performed using fetal blood can now be done using DNA-based analysis of chorionic villi PUBS involves insertion of needle directly into fetal umbilical vessel, preferably the vein under ultrasound guidance The most common genetic indication: evaluation of mosaic results found on amniocentesis or CVS when a sample of fetal blood is required to determine the specific mutation Also used to assess for fetal anemia, infection, thrombocytopenia Bleeding from the cord puncture site is the most common complication of the procedure Transient fetal bradycardia can also occur Maternal complications are rare but include amnionitis and transplacental hemorrhage Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Maternal Assays Alpha-Fetoprotein Used as a screening tool for NTDs in pregnancy – for NTDs and open abdominal wall defects Risk factors for NTDs: history of this disorder in prior pregnancy, folic acid deficiency, pregestational diabetes, teratogen exposure (valproic acid (Depakote), carbamazepine (Tegretol)) AFP is produced in the fetal gastrointestinal tract and liver and increasing levels are detectable in serum of pregnant women from 14-34 weeks gestation. Although amniotic fluid AFP measurement is diagnostic for NTD, maternal serum AFP is a screening tool only — maternal serum AFP (MSAFP) performed between 15-20 weeks gestation (ideal 16-18) Once determined, compared with normal values for each week of gestation Values should correlate with maternal age, weight, race, presence of multifetal pregnancy, whether woman has insulin-dependent diabetes When MSAFP level elevated, obtain fluid through amniocentesis to determine amniotic fluid AFP and acetylcholinesterase levels as standard follow-up testing Targeted ultrasound for identifying NTD as amniotic fluid AFP and acetylcholinesterase measurements Multiple Marker Screens Screening to detect fetal chromosomal abnormalities trisomy 21 Down at 11-14 weeks of gestation The first-trimester screen includes measurement of two maternal biochemical markers: pregnancy-associated placental protein A (PAPP-A) and human chorionic gonadotropin (hCG) or the free beta-human chorionic gonadotropin (beta-hCG) subunit and evaluation of fetal nuchal translucency (NT) or a combination of both In the presence of a fetus with trisomy 21, hCG levels and NT measurement are higher than normal in the first trimester, whereas PAPP-A levels are lower than normal First-trimester screening PAPP-A and hCG or beta-hCG levels has been shown to be as accurate for detecting fetuses with trisomy 21 as triple screening in the second trimester Another biochemical marker that can be measure during the first trimester, at 8-10 weeks of gestation is disintegrin and metalloproteinase 12 (ADAM 12) a glycoprotein that is synthesized by the placenta and secreted throughout pregnancy Decreased levels of ADAM 12 are found in women carrying a fetus with trisomy 21 About 1/3 of all fetuses with an increased NT have a chromosomal abnormality; 1/2 have trisomy 21 Combining serum marker and NT values results in detection of Down – results are comparable to those obtained with quad screening in the second trimester Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Another way to predict trisomy 21 - assessment of fetal nasal bone by ultrasound during the first trimester Nasal bone cannot be identified on ultrasound in about 1/4 to 1/3 of fetuses who have trisomy 21 In the second trimester, triple screening and quad screening are available to screen for fetuses with trisomy 21 and trisomy 18 The triple-marker screen, performed at 16 to 18 weeks of gestation, measures the levels of three maternal serum markers: MSAFP, unconjugated estriol, and hCG In the presence of a fetus with trisomy 21, the MSAFP and unconjugated estriol levels are low, whereas the hCG level is elevated Low values in all three markers are associated with trisomy 18 The quad screen adds an additional marker — placental hormone called inhibin A to increase accuracy for screening for Down syndrome in women younger than 35 Elevated inhibin A level indicate possibility of Down Addition of inhibin A to other three markers increases the detection rate for Down syndrome to about 75% in women younger than 35 years of age Similar to the triple marker screening, the optimal time to perform the quad screen is between 16 to 18 weeks of gestation The ability of multiple marker test to detect chromosomal abnormalities depends on accuracy of gestational age assessment — screening only not diagnostic Women with positive test should be offered diagnostic testing by amniocentesis or CVS for fetal karyotyping Coombs Test Indirect Coombs screening test is a screening tool for Rh incompatibility If maternal titer for Rh antibodies is greater than 1 : 8 → amniocentesis for determination of bilirubin in amniotic fluid is indicated to establish severity of fetal hemolytic anemia ○ Now middle cerebral artery Doppler studies to determine degree of fetal hemolysis have replaced serial amniocentesis Coomb test can also detect other antibodies that may place fetus at risk for incompatibility with maternal antigens Cell-Free (DNA) Screening Newest screening test for aneuploidy performed using sample of a maternal blood cfDNA screening test is an example of noninvasive prenatal testing (NIPT) Provides definitive diagnosis for fetal Rh status, fetal gender, certain paternally transmitted single gene disorders Aneuploidy is defined as having one or more extra or missing chromosomes in the 23 pairs (normally) Common aneuploidies are trisomies 13, 18, 21 – results from an extra chromosome Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Maternal plasma contains small fragments of cfDNA resulting from breakdown of both maternal and fetal cells – normal amounts vary throughout pregnancy Test cannot distinguish fetal from maternal DNA but can accurately predict fetal status by measuring amount of cfDNA circulating in maternal blood and comparing it w known standards If fetus has normal karyotype, the amount of DNA is consistent with the known standard for the normal amount If more than expected amount of chromosome 21 DNA is detected → fetus is contributing extra amount and has trisomy 21 → Down syndrome !! screening test so if screening is positive → amniocentesis and CVS to confirm findings !! Accuracy of the test depends on proportion of fetal to maternal DNA in maternal plasma which must be at least 4% As pregnancy progresses, fetal contribution to amount of cfDNA in maternal circulation increases cfDNA screening for detection of fetal chromosomal abnormalities: optimally performed at 10-12 weeks by which time the average fetal DNA fraction should have reached approximately 10% of maternal DNA Test is offered to women considered to be at risk for chromosomal abnormalities (aneuploidies) including those with advanced maternal age, screen-positive maternal serum screens, ultrasound abnormalities, women who have given birth to a child with chromosomal abnormality cfDNA test is simple to perform → sample of maternal blood is obtained by venipuncture and sent to commercial laboratory Test is less sensitive in women who are obese Currently not recommended for use in multifetal pregnancies Antepartum Assessment Using Electronic Fetal Monitoring Indications First and second-trimester antepartum assessment is directed primarily at the diagnosis of fetal anomalies Third-trimester testing is to determine whether intrauterine environment continues to support the fetus Testing is often used to determine the timing of childbirth for women at risk for interrupted oxygenation to the fetus by any of several mechanisms The ability to detect and prevent impending fetal death depends on the group of pregnant women selected for testing, the predictive value of the tests used, the clinician’s ability to respond to abnormal test results Maternal assessment of fetal movement is suggested as a first-line screening test for fetal well-being Initial testing begin at 32-34 weeks gestation and performed once or twice weekly When electronic fetal monitoring and ultrasound are used for antepartum fetal evaluation, nonstress test and modified biophysical profile (mBPP) are the primary tests performed Complete BPP and contraction stress test are follow-up evaluation in patients who have persistently nonreactive nonstress test or abnormal mBPP score Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Nonstress Test Noninvasive antepartum evaluation of the fetus Basis for NST is that normal fetus produces characteristic heart rate patterns in response to fetal movement, uterine contraction, or stimulation Quiet fetal sleep state, CNS depressant medications, chronic smoking, presence of fetal malformation can adversely affect the test Disadvantage: requirement for twice-weekly testing, high false-positive rate, higher false-negative rate Procedure 20-30 mins; FHR recorded with a Doppler transducer, tocodynamometer applied to detect uterine contractions or fetal movements – tracing observed for signs of fetal activity and concurrent accelerations of FHR – movement detected on tracing Vibroacoustic stimulation is often used to change fetal state from quiet to active sleep if initial NST result is nonreactive Interpretation NST results are either reactive or nonreactive Reactive NST is considered normal – nonreactive need further evaluation Testing period is often extended for 20 minutes with expectation that fetal sleep state will change and test will be more reactive If test does not meet criteria after 40 minutes, then need contraction stress test or BPP Once NST is initiated, it is usually repeated once or twice weekly for the remainder of the pregnancy Reactive Test: Two accelerations in a 20-minute period, each lasting at least 15 seconds and peaking at least 15 beats/min above the baseline Before 32 weeks of gestation, an acceleration is defined as a rise of at least 10 beats/min lasting at least 10 seconds from onset to offset Nonreactive Test: A test that does not demonstrate at least two qualifying accelerations within a 20-minute window Contraction Stress Test Oxytocin challenge test – electronic fetal assessment test Devised as a graded stress test of fetus and its purpose was to identify the jeopardized fetus that was stable at rest but showed evidence of compromise after stress Uterine contractions decrease uterine blood flow and placental perfusion If this decrease is sufficient to produce hypoxia in the fetus, a deceleration in FHR results Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 !! In a healthy fetoplacental unit, uterine contractions do not usually produce late decelerations, whereas if interrupted oxygenation is present, contractions produce late decelerations !! CST provides earlier warning of fetal compromise than NST and produces fewer false-positive results Cannot predict acute fetal compromise (umbilical cord accident, placental abruption, rapid deterioration of glucose control in women with diabetes) CST is more time consuming and expensive than NST Also an invasive procedure if oxytocin stimulation is required Contraindications: preterm labor, placenta previa, vasa previa, cervical insufficiency, multiple gestation, previous classical uterine incision for cesarean birth – it is a backup rather than primary method of antepartum testing Procedure Monitored electronically with fetal ultrasound transducer and uterine tocodynamometer Tracing is observed for 10-20 minutes for baseline rate and variability and the possible occurrence of spontaneous contractions Two methods are nipple-stimulated contraction and more commonly oxytocin-stimulated contraction test Nipple-Stimulated Contraction Test In one approach: woman applies warm moist washcloth to both breasts for several minutes – massage one nipple for 10 minutes Massaging nipple causes release of oxytocin from posterior pituitary gland Alternative approach: massage one nipple through clothes for 2 minutes, rest for 5 minutes, repeat cycle of massages and rest as necessary to achieve adequate uterine activity When adequate contractions or hyperstimulation (defined as uterine contractions lasting more than 90 seconds or five or more contractions in 10 minutes) occurs, stimulation should be stopped Oxytocin-Stimulated Contraction Test Exogenous oxytocin can be used to stimulate uterine contraction An intravenous (IV) infusion is begin and a dilute solution of oxytocin is infused into the tubing of the main IV line through a piggyback port and delivered by an infusion pump to ensure an accurate dose One method of oxytocin infusion is to begin at 0.5 milliunits/min and double the dose every 20 minutes until three uterine contractions of moderate intensity, each lasting 40-60 seconds, are observed within a 10-minute period These criteria for contractions were selected to approximate the stress experience by the fetus during the first stage of labor Downloaded by Craig Cman ([email protected]) lOMoARcPSD|15450111 Interpretation Can be negative, positive, equivocal, suspicious or unsatisfactory If no late decelerations are observed within contraction, findings are considered negative Repetitive late decelerations render test results positive The desired CST result is negative because it has consistently been associated with good fetal outcomes Positive CST results have been associated with intrauterine fetal death, late FHR decelerations in labor, IUGR, meconium-stained amniotic fluid Usually leads to hospitalization for further close observation or birth Interpretation of the Contract Stress Test Interpretation Clinical Significance Negative At least 3 uterine contractions in a 10-min period, Usually resume routine weekly schedule with no late or significant variable deceleration Positive Late decelerations occur with 50% or more of Usually warrants hospital admission for further contractions, even if there are fewer than 3 evaluation and/or delivery contractions in 10 mins Suspicious or Equivocal Prolonged, variable, or late decelerations occurring Further evaluation needed, either by prolonged with less than 50% of the contractions monitoring or repeat testing the next day Equivocal-Hyperstimulatory Decelerations that occur in the presence of Further evaluation needed, either by prolonged contractions more frequent than every 2 mins or monitoring or repeat testing the next day lasting longer than 90 secs Unsatisfactory Failure to produce 3 contractions within a 10-min Further evaluation needed, either by prolonged window or inability to trace the fetal heart rate monitoring or repeat testing the next day Downloaded by Craig Cman ([email protected])