Postdates and antenatal testing

The standard definition of a prolonged pregnancy is 42 completed weeks of gestation. The incidence of prolonged pregnancy varies depending on the criteria used to define gestational age at birth. It is estimated that 4 to 19% of pregnancies reach or exceed 42 weeks gestation. Several studies that have used very large computerized databases of well-dated pregnancies provided insights into the incidence and nature of adverse perinatal outcome such as an increased fetal and neonatal mortality as well as increased fetal and maternal morbidity in prolonged pregnancy. Fetal surveillance may be used in an attempt to observe the prolonged pregnancy while awaiting the onset of spontaneous labor. This article reviews the different methodologies and protocols for fetal surveillance in prolonged pregnancies. On the one hand, false-positive tests commonly lead to unnecessary interventions that are potentially hazardous to the gravida. On the other hand, to date, no program of fetal testing has been shown to completely eliminate the risk of stillbirth.     

Antenatal testing: diabetes mellitus

Diabetes complicating pregnancy is a problem for which fetal surveillance testing is considered to be the standard of care. In response to the unacceptable frequency of stillbirth in such pregnancies, fetal testing historically was first introduced to manage women whose pregnancies were complicated by diabetes. Essentially all forms of antepartum testing have been used to assess fetal well-being during the third trimester of pregnant diabetics. The contraction stress test became established as the "gold standard," yet other testing protocols have been used successfully. It is clear that control of diabetes throughout gestation, not just in the later stages, is more important for optimal outcome than is a specific form of fetal testing. Biweekly testing has become the standard and with well-controlled diabetics, allowing the gestation to continue until the onset of spontaneous labor, even when the gestation exceeds 40 weeks, is appropriate management with normal testing.     

The risk of unexplained antepartum stillbirth in second pregnancies following caesarean section in the first pregnancy

Objective  To determine if a previous caesarean section increases the risk of unexplained antepartum stillbirth in second pregnancies.
Study design  Retrospective cohort study.
Setting  Large Canadian perinatal database.
Population  158 502 second births.
Methods  Data were obtained from a large perinatal database, which supplied data on demographics, pregnancy complications, maternal medical conditions, previous caesarean section and pregnancy outcomes.
Main outcome measures  Total and unexplained stillbirth.
Results  The antepartum stillbirth rate was 3.0/1000 in the previous caesarean section group compared with 2.7/1000 in the previous vaginal delivery group ( P = 0.46). Multivariate logistic regression modelling, including terms for maternal age (polynomial), weight >91 kg, smoking during pregnancy, pre-pregnancy hypertension and diabetes, did not document an association between previous caesarean section and unexplained antepartum stillbirth (OR 1.27, 95% CI 0.92–1.77).
Conclusion  Caesarean section in the first birth does not increase the risk of unexplained antepartum stillbirth in second pregnancies.     

Maternal medical disease: risk of antepartum fetal death

Although certain maternal medical conditions increase the risk of antepartum fetal death, improvements in medical and obstetric care have decreased the likelihood of stillbirth. This article examines the current stillbirth rates reported in pregnancies complicated by common medical diseases. The reported stillbirth rates are expressed as the number of stillbirths occurring at > or = 20 weeks of gestation per 1,000 births in patients with the condition. Overall, about 10% of all fetal deaths are related to maternal medical illnesses such as hypertension, diabetes, obesity, systemic lupus erythematosus, chronic renal disease, thyroid disorders, and cholestasis of pregnancy. The early recognition of maternal medical diseases provides an opportunity for increased surveillance and interventions that may lead to more favorable pregnancy outcomes.     

Antepartum fetal health

Delivery of a healthy full term baby following an uneventful antenatal period occurs in the majority of pregnancies. These are classified as a low-risk pregnancy group. There are, however, some pregnancies that are complicated due to maternal or fetal disease that can increase the risk of perinatal morbidity and mortality. This is classified as a high-risk group. The aim of fetal surveillance is to identify these threatened fetuses with the prospect of altering the timing of delivery to prevent the worst outcome, stillbirth. This article looks at the tools available to assess antenatal fetal health in all pregnancies and their ability to identify the at-risk pregnancies that require extra surveillance to improve outcomes. This article does not address fetal surveillance during labour.     

Clinical implications from monitoring fetal activity

The monitoring of fetal motion in high-risk pregnancies has been shown to be worthwhile in predicting fetal distress and impending fetal death. The maternal recording of perceived fetal activity is an inexpensive surveillance technique which is most useful when there is chronic uteroplacental insufficiency or when a stillbirth may be expected. The presence of an active, vigorous fetus is reassuring, but documented fetal inactivity required a reassessment of the underlying antepartum complication and further fetal evaluation with real-time ultrasonography, fetal heart rate testing, and biochemical testing. Fetal distress from such acute changes as abruptio placentae or umbilical cord compression may not be predicted by monitoring fetal motion. Although not used for routine clinical investigation, electromechanical devices such as tocodynamometry have provided much insight into fetal behavioral patterns at many stages of pregnancy and in pregnancies with an antepartum complication.     

Should older women have antepartum testing to prevent unexplained stillbirth?

OBJECTIVE: Older women are at an increased risk for unexplained stillbirth late in pregnancy. The purpose of this study was to compare 3 strategies for the prevention of unexplained fetal death in women aged 35 years and older. We compared usual care (no antepartum testing or induction before 41 weeks), weekly testing at 37 weeks with induction after a positive test, and no testing with induction at 41 weeks. METHOD: We used a Markov model to quantify the risks and benefits of each strategy in terms of the number of antepartum tests, inductions, and additional cesarean deliveries per fetal death averted. Probability data used in the model were derived from obstetrical databases and the literature. RESULTS: Without a strategy of antepartum surveillance between 37 and 41 weeks, women aged 35 years and older would experience 5.2 unexplained fetal deaths per 1,000 pregnancies. For nulliparous women 35 and older, weekly antepartum testing initiated at 37 weeks would avert 3.9 fetal deaths per 1,000 pregnancies but would require 863 antepartum tests, 71 inductions, and 14 additional cesarean deliveries per fetal death averted. A strategy of no testing but induction at 41 weeks would avert 0.9 fetal deaths per 1,000 pregnancies and require 469 inductions and 219 additional cesareans per fetal death averted. CONCLUSION: A strategy of antepartum testing in older women would reduce the number of unexplained stillbirths at term and would result in fewer inductions and cesareans per fetal death averted than a strategy of no antepartum testing but induction at 41 weeks.     

Management of pregnancy complications in women of advanced maternal age

The average age of women at childbirth in high resource obstetric settings has been increasing steadily for approximately 30 years. Women aged 35 years or over have an increased risk of gestational hypertensive disease, gestational diabetes, placenta praevia, placental abruption, perinatal death, preterm labour, fetal macrosomia and fetal growth restriction. Unsurprisingly, rates of obstetric intervention are higher among older women. Of particular concern is the increased risk of antepartum stillbirth at term in women of advanced maternal age. In all maternal age groups, the risk of stillbirth is higher among nulliparous women than among multiparous women. Women of advanced maternal age (>40 years) should be given low dose aspirin in the presence of an additional risk factor for pre-eclampsia and offered serial ultrasounds for fetal growth and wellbeing. Given the increased risk of antepartum stillbirth, induction of labour from 39 weeks’ gestation should be discussed with woman.     

Advanced maternal age

The average age of women at childbirth in industrialised nations has been increasing steadily for approximately 30 years. Women aged 35 years or over have an increased risk of gestational hypertensive disease, gestational diabetes, placenta praevia, placental abruption, perinatal death, preterm labour, fetal macrosomia and fetal growth restriction. Unsurprisingly, rates of obstetric intervention are higher among older women. Of particular concern is the increased risk of antepartum stillbirth at term in women of advanced maternal age. In all maternal age groups, the risk of stillbirth is higher among nulliparous women than among multiparous women. Women of advanced maternal age (>40 years) should be given low dose aspirin (in the presence of an additional risk factor for pre-eclampsia) and offered serial ultrasounds for fetal growth and wellbeing; given the increased risk of antepartum stillbirth, induction of labour from 39 weeks’ gestation should be discussed with the woman.     

Antepartum fetal surveillance and timing of delivery in the pregnancy complicated by diabetes mellitus

Pregnancies complicated by diabetes mellitus are associated with an increased risk of fetal and neonatal risks compared with pregnancies in the healthy gravida. Data suggest that stillbirth and perinatal mortality may be increased as much as 5 times for patients with insulin-dependent diabetes than in the general population. Pregnancies complicated by preexisting diabetes should undergo twice weekly surveillance with nonstress test or biophysical profile or a combination of both. Doppler studies should be reserved for those patients with vascular disease, intrauterine growth restriction, or hypertensive disorders.     

Should Assessment of Amniotic Fluid Volume Form an Integral Part of Antenatal Fetal Surveillance of High Risk Pregnancy?

Summary: This study was conducted to evaluate the role of the Amniotic Fluid Index (AFI), used along with nonstress cardiotocography (NST) and fetal acoustic stimulation test (FAST), when required, in prediction of adverse pregnancy outcome. Over a 3-year period 565 pregnant women had antepartum fetal surveillance due to various high risk pregnancy factors and delivered within 7 days of the test. Antepartum fetal surveillance included nonstress cardiotocography together with estimation of AFI. Need for induction of labour, presence of meconium at rupture of membranes, Caesarean section for fetal distress, Apgar score at 5 minutes, need for neonatal endotracheal intubation, admission to neonatal special care unit and perinatal death were the main outcome measures.
Nonreactive nonstress tests and Caesarean sections for fetal distress were more common and neonatal outcome was significantly poorer in patients with AFI < 5 cm than in those with higher AFI values. Of the 4 perinatal deaths in the group with AFI < 5 cm, 3 had a reactive NST within 7 days of fetal death.
It is concluded that pregnancy outcome is often poor in the presence of very low AFI and in these cases a reactive NST loses its usual reassuring value. It is suggested that AFI estimation should be included as an integral part of antepartum fetal surveillance of high risk pregnancies.     

The effectiveness of antepartum surveillance in reducing the risk of stillbirth in patients with advanced maternal age

Objective

To estimate the effectiveness of antepartum surveillance and delivery at 41 weeks in reducing the risk of stillbirth in advanced maternal age (AMA) patients.

Study design

Retrospective cohort study of all patients managed in one maternal–fetal medicine practice from June 2005 to May 2012. We included all singleton pregnancies delivered at ≥20 weeks of gestation. All AMA patients (age ≥35 years at their estimated delivery date) underwent weekly biophysical profile testing beginning at 36 weeks, as well as planned delivery at 41 weeks, or sooner if indicated. We compared the rate of fetal death at ≥20 weeks and fetal death at ≥36 weeks in AMA vs. non-AMA patients. Fetal deaths due to lethal and chromosomal abnormalities were excluded.

Results

4469 patients met the inclusion criteria: 1541 (34.5%) were AMA and 2928 (65.5%) were non-AMA. Using our AMA protocol for surveillance and timing of delivery, the incidence of stillbirth was similar to the non-AMA population (stillbirth ≥20 weeks: 3.9 per 1000 vs. 3.4 per 1000, p = 0.799; stillbirth ≥36 weeks: 1.4 per 1000 vs. 1.1 per 1000, p = 0.773). When looking at women age <35, age 35–39, and age ≥40, the incidence of stillbirth ≥20 weeks and ≥36 weeks did not increase across the three groups. Our findings were similar when we excluded all patients with other indications for antepartum surveillance.

Conclusions

In AMA patients, antepartum surveillance and delivery at 41 weeks appears to reduce the risk of stillbirth to that of the non-AMA population. Routine antepartum surveillance should be considered in all AMA patients.     

Subsequent birth outcomes after an unexplained stillbirth: preliminary population-based retrospective cohort study

The objective of this study was to determine whether women who have experienced an unexplained stillbirth have a higher risk of adverse perinatal outcomes in subsequent births. We compared 316 subsequent births to women with a previous unexplained stillbirth, with 3160 births to women with no previous history of stillbirth, matched by year of birth, in the period 1987-1997, from the South Australian perinatal database, using logistic regression analysis. There was no increase in the rate of stillbirth and no statistically significant increase in the rate of perinatal death (OR 1.62 [95%CI 0.63-4.20]) or neonatal death, although larger studies are needed to confirm this. However, after adjusting for age, parity, and hospital category of birth, women who had a previous stillbirth had increased incidences in subsequent births of abnormal glucose tolerance or gestational diabetes (a fourfold increase); induction of labour and elective Caesarean section; fetal distress and postpartum haemorrhage; and forceps and emergency Caesarean delivery and preterm birth, which were independent of induction of labour. Gestational age at birth and birthweight were also significantly reduced, suggesting a need for close monitoring of their future pregnancies.     

Stillbirth: a review.

Stillbirth occurs in nearly 1% of all births in the USA, and is one of the most common but least studied adverse pregnancy outcomes. The many risk factors for and causes of stillbirth are presented. Over the past several decades, the rate of stillbirth has been substantially reduced, with the reduction most apparent in those stillbirths previously occurring at term and/or in labor. Reductions have occurred because of reductions in risk factors (i.e. prevention of Rh disease and better control of diabetes), better antepartum monitoring of those with risk factors followed by early delivery for those fetuses found to be at risk (i.e. growth restriction, maternal pre-eclampsia), better intrapartum fetal monitoring, increases in Cesarean section for those at risk, and early detection of congenital anomalies followed by termination prior to the time that these early fetal deaths are classified as stillbirths. Finally, the value of using fetal autopsy and placental examination to determine the cause of death accurately, both for research purposes and for patient counseling in future pregnancies, is explored.     

Life-table analysis of the risk of perinatal death at term and post term in singleton pregnancies

OBJECTIVE: This study was undertaken to estimate the cumulative risk of perinatal death associated with delivery at each gestational week both at term and post term. STUDY DESIGN: The numbers of antepartum stillbirths, intrapartum stillbirths, neonatal deaths, and surviving neonates delivered at between 37 and 43 weeks' gestation in Scotland, 1985-1996, were obtained from national databases (n = 700,878) after exclusion of multiple pregnancies and deaths caused by congenital abnormality. The numbers of deaths at each gestational week were related to appropriate denominators: antepartum stillbirths were related to ongoing pregnancies, intrapartum stillbirths were related to all births (excluding antepartum stillbirths), and neonatal deaths were related to live births. The cumulative probability of perinatal death associated with delivery at each gestational week was estimated by means of life-table analysis. RESULTS: The gestational week of delivery associated with the lowest cumulative risk of perinatal death was 38 weeks' gestation, whereas the perinatal mortality rate was lowest at 41 weeks' gestation. The risk of death increased more sharply among primigravid women after 38 weeks' gestation because of a greater risk of antepartum stillbirth. The relationships between risk of death and gestational age were similar for the periods 1985-1990 and 1991-1996. CONCLUSION: Delivery at 38 weeks' gestation was associated with the lowest risk of perinatal death.     

Restricted fetal growth in sudden intrauterine unexplained death

BACKGROUND: Unexplained antepartum stillbirth is a common cause of perinatal death, and identifying the fetus at risk is a challenge for obstetric practice. Intrauterine growth restriction (IUGR) is associated with a variety of adverse perinatal outcomes, but reports on its impact on unexplained stillbirths by population-based birthweight standards have been varying, including both unexplained and unexplored stillbirths. AIM: We have studied IUGR, assessed by individually adjusted fetal weight standards, in antepartum deaths that remained unexplained despite thorough postmortem investigations. METHODS: Antenatal health cards from a complete population-based 10-year material of 76 validated sudden intrauterine unexplained deaths were compared to those of 582 randomly selected liveborn controls. Birthweight <10th percentile of the individualized standard adjusted for gestational age, maternal height, weight, parity, ethnicity, and fetal gender was defined as growth restriction. RESULTS: 52% of unexplained stillbirths were growth restricted, with a mean gestational age at death of 35.1 weeks. Suboptimal growth was the most important fetal determinant for sudden intrauterine unexplained death (odds ratio 7.0, 95% confidence interval 3.3-15.1). Concurrent maternal overweight or obesity, high age, and low education further increase the risk. Overweight and obesity increase the risk irrespective of fetal growth, and while high maternal age increases the risk of the normal weight fetus, it is not associated to growth restriction as a precursor of sudden intrauterine unexplained death. CONCLUSIONS: IUGR is an important risk factor of sudden intrauterine unexplained death, and this should be excluded in pregnancies with any other risk factor for sudden intrauterine unexplained death.     

Prediction and prevention of recurrent stillbirth

Stillbirth is one of the most common adverse pregnancy outcomes in the United States, occurring in one out of every 200 pregnancies. There is a paucity of information on the outcome of pregnancies after stillbirth. Prior stillbirth is associated with a twofold to 10-fold increased risk of stillbirth in the future pregnancy. The risk depends on the etiology of the prior stillbirth, presence of fetal growth restriction, gestational age of the prior stillbirth, and race. Categorization of the cause of the initial stillbirth will allow better estimates of individual recurrence risk and guide management. A history of stillbirth also increases the risk of other adverse pregnancy outcomes in the subsequent pregnancy such as placental abruption, cesarean delivery, preterm delivery, and low birth weight infants. Prospective studies have revealed an increased risk of stillbirth with low pregnancy-associated plasma protein A, elevated maternal serum alpha fetoprotein, abnormal uterine artery Doppler studies, and antiphospholipid antibodies. However, the positive predictive value of these factors individually is poor. Because fetal growth restriction is associated with almost half of all stillbirths, the correct diagnosis of fetal growth restriction is essential. The use of individualized or customized growth standards will improve prediction of adverse pregnancy outcome by distinguishing growth-restricted fetuses from constitutionally small, healthy fetuses. Antepartum fetal surveillance and fetal movement counting are also mainstays of poststillbirth pregnancy management.     

The role of human placental lactogen assays in antepartum fetal assessment

To determine the role of hPL radioimmunoassays in screening for fetal assessment in normal and hypertensive pregnancies the results of 148 pregnancies were examined by measuring the specificity and sensitivity of the test for prospectively defined fetal conditions. Values of hPL were considered abnormal if they were below the tenth percentile for the range of values derived from pregnancies with a normal fetal outcome (<3.8 μg/ml). The specificity of the test was 95% but it would have correctly predicted a normal fetal outcome in only 85% of pregnancies. The test varied in its ability to accurately predict abnormal fetal outcome; the sensitivity for the single stillbirth and for cases of fetal jeopardy was 87%, whereas for IUGR the result was 41%. There was a significant difference between hPL values associated with fetal jeopardy and uncomplicated IUGR (p < 0.01). The frequency of sampling and the application of these results to the prospective screening of normal and hypertensive pregnancies is discussed and it is concluded that hPL assays have a limited but specific role in antepartum evaluation. Screening should be reserved for pregnancies associated with hypertension to exclude the risk of stillbirth and fetal jeopardy occurring specifically in the IUGR fetus.     

死胎病因及管理

死胎的主要原因包括妊娠前母体疾病,如糖尿病,以及妊娠期并发症,如产前出血、妊娠期肝内胆汁淤积症、胎儿生长受限、单绒毛膜双胎、感染等。脐动脉彩色超声多普勒有助于预测死胎病因。小剂量阿司匹林（60～80 mg）有助于预防高危妊娠孕妇发生子痫前期及其他不良围生期结局。死胎尸检、胎盘病理检查和胎母出血检测等是死胎病因检查的基本手段。     

Effects of monitoring high-risk pregnancies and intrapartum FHR monitoring on perinates.

A protocol of chronic antepartum surveillance was initiated at the University of Illinois hospitals in 1973 to assess the impact on perinatal mortality. At the same time, a policy of unselected fetal heart rate (FHR) monitoring was initiated to judge the effect on the intrapartum stillbirth rate. The impact of both programs played a significant role in the decline of perinatal mortality rates for infants weighing more than 1 500 g, from 21.1/1 000 births in 1970--1971 to 14.4/1 000 births in the monitored years 1973 and 1974 (p less than 0.02).