Postdate fetal surveillance: is 41 weeks too early?

During an 18-month period, 293 patients had a nonstress test and ultrasonographic evaluation of amniotic fluid volume twice weekly beginning at 41 weeks' gestation. Patients were admitted for induction of labor for either an abnormal nonstress test result or oligohydramnios. A control population consisted of 59 low-risk patients who were delivered between 39 and 41 weeks' gestation and had antepartum testing within 4 days of delivery. Study patients who were delivered between 41 and 42 weeks' gestation had a significantly increased incidence of abnormal nonstress tests, oligohydramnios, cesarean sections for fetal distress, and admissions to the neonatal intensive care unit compared with control patients. The abnormal fetal testing and adverse perinatal outcome associated with pregnancies over 42 weeks were also found in pregnancies between 41 and 42 weeks' gestation. These data support the concept that postdate fetal testing should begin at 41 weeks of gestation.     

Antepartum fetal monitoring in insulin-dependent diabetic pregnancies

In order to minimize unexplained stillbirths in insulin-dependent diabetic pregnancies, fetal well-being was assessed by antepartum monitoring while development of pulmonary maturity was awaited. Antepartum monitoring consisted of outpatient nonstress tests beginning at 32 weeks' gestation. Fetuses with nonreactive nonstress tests were further evaluated by contraction stress tests and were delivered if tests were positive. With use of this system there were no unexplained stillbirths during management of 119 insulin-dependent diabetic pregnancies. Of 14 infants delivered because of positive contraction stress tests, six were found to have major disorders; the other eight had no major residual neonatal morbidity. Thus this system of antepartum fetal surveillance: eliminated unexplained stillbirths, identified a subgroup of insulin-dependent diabetic pregnancies with a high rate of major fetal abnormalities, and allowed for identification and subsequent timely delivery of the other distressed fetuses that were at a high risk of neonatal morbidity and/or mortality, such that potential long-term adverse outcomes were avoided.     

Previous stillbirth, late preterm, and early-term birth

Subsequent pregnancies are emotionally traumatic for families with previous stillbirths. Such pregnancies have a 2- to 10-fold increase in the risk for stillbirth as well as an increased probability of other adverse obstetrical outcomes. These medical risks as well as anxiety on the part of families and care providers contribute to an increase in late preterm and early-term birth. However, delivery before 39 weeks' gestation has not been proven to reduce the risk of recurrent stillbirth or adverse pregnancy outcomes in women with previous stillbirths. This work reviews data regarding the optimal timing of delivery in subsequent pregnancies after previous stillbirth, as well as for patients at risk from stillbirth in general. Management recommendations from current data are presented and knowledge gaps are highlighted.     

Prospective risk of stillbirth.

Some fraction of any cohort of fetuses alive at a given gestational age will ultimately die before birth. The residual prospective risk of stillbirth as a function of gestational age was calculated from records of the New York City Department of Health covering 370,051 reported births between 1987-1989, including 2454 stillbirths. In the general population, the prospective risk of stillbirth at 26 weeks was one in 150 and, because the time distributions of live births and stillbirths were not proportionate, the risk changed with gestational age. By 40 weeks' gestation, it was one in 475, rising progressively thereafter to one in 375 at 43 weeks. The prospective risk of stillbirth was elevated in certain ethnic groups and increased significantly with advanced maternal age, multiple gestation, and lack of prenatal care. The prospective risk of stillbirth is an important consideration in decisions regarding timing of delivery.     

Gestational age and fetal biophysical assessment

With improved neonatal care, biophysical assessment to detect fetal asphyxia is used increasingly at an earlier gestational age. We have tested five fetal biophysical variables: nonstress test, fetal breathing movements, fetal movements, fetal tone, and amniotic fluid volume 11,012 times in 5582 singleton fetuses in whom there was a normal perinatal outcome. The nonstress test and fetal breathing movements were more likely to be abnormal at 26 to 33 weeks' gestation compared with 34 to 41 weeks. The nonstress test, fetal breathing movements, fetal tone, and amniotic fluid volume were more likely to be abnormal at 42 to 44 weeks' gestation compared with 37 to 41 weeks. Fetal biophysical tests should be interpreted in relation to gestational age.     

Screening for fetal well-being in a high-risk pregnant population comparing the nonstress test with umbilical artery Doppler velocimetry: a randomized controlled clinical trial

OBJECTIVE: The purpose of this study was to evaluate the ability of two different modes of antepartum fetal testing to screen for the presence of peripartum morbidity, as measured by the cesarean delivery rate for fetal distress in labor. STUDY DESIGN: Over a 36-month period, all patients who were referred to the Fetal Assessment Unit at BC Women's Hospital because of a perceived increased fetal antepartum risk at a gestational age of > or =32 weeks of gestation were approached to participate in this study. Fetal surveillance of these women was allocated randomly to either umbilical artery Doppler ultrasound testing or nonstress testing as a screening test for fetal well-being. If either the umbilical artery Doppler testing or the nonstress testing was normal, patients were screened subsequently with the same technique, according to study protocol. When the Doppler study showed a systolic/diastolic ratio of >90th percentile or the nonstress testing was equivocal (ie, variable decelerations), an amniotic fluid index was performed, as an additional screening test. When the amniotic fluid index was abnormal (<5th percentile), induction and delivery were recommended. When the Doppler study showed absent or reversed diastolic blood flow or when the nonstress test result was abnormal, induction and delivery were recommended to the attending physician. Statistical comparisons between groups were performed with an unpaired t test for normally distributed continuous variables and chi(2) test for categoric variables. RESULTS: One thousand three hundred sixty patients were assigned randomly to groups in the study; 16 patients were lost to follow up. Six hundred forty-nine patients received Doppler testing and 691 received nonstress testing. The mean number of visits for the Doppler test and nonstress test groups was two versus two, respectively. The major indications for fetal assessment included postdates (43%), decreased fetal movement (22%), diabetes mellitus (11%), hypertension (10%), and intrauterine growth restriction (7%). The incidence of cesarean delivery for fetal distress was significantly lower in the Doppler group compared with the nonstress testing group (30 [4.6%] vs 60 [8.7%], respectively; P <.006). The greatest impact on the reduction in cesarean deliveries for fetal distress was seen in the subgroups in which the indication for testing was hypertension and suspected intrauterine growth restriction. CONCLUSION: Umbilical artery Doppler as a screening test for fetal well-being in a high-risk population was associated with a decreased incidence of cesarean delivery for fetal distress compared to the nonstress testing, with no increase in neonatal morbidity.     

Improved outcome of twice weekly nonstress testing

The nonstress test is a commonly used tool for fetal well-being assessment. The antenatal death rate using the nonstress test as a primary modality is significantly higher than that with the use of the contraction stress test. The nonstress test is commonly performed on a once-a-week basis. The rate of stillbirths with reactive nonstress tests, performed once a week, was 6.1 per 1000 in the author's previously published report. Nonstress tests were performed on a twice-a-week basis beginning January 1981, and results are reported on 913 such patients. The rate of stillbirths with reactive nonstress tests was reduced to 1.9 per 1000 in this second group. It is suggested that the patients who are at risk for fetal stress should be evaluated on a twice-a-week basis when the nonstress test is used as the primary test.     

Racial and ethnic disparities in United States: stillbirth rates: trends, risk factors, and research needs

As with most adverse health outcomes, there has been long standing and persistent racial and ethnic disparity for stillbirth in the United States. In 2005, the stillbirth rate (fetal deaths ≥ 20 weeks' gestation per 1000 fetal deaths and live births) for non-Hispanic blacks was 11.13 compared with 4.79 for non-Hispanic whites. Rates were intermediate for American Indian or Alaska Natives (6.17) and Hispanics (5.44). There is racial disparity for both early (< 28 weeks' gestation) and late stillbirths. We review available data regarding risk factors for stillbirth with a focus on those factors that are more prevalent in certain racial/ethnic groups and those factors that appear to have a more profound effect in certain racial/ethnic groups. Although many factors, including genetics, environment, stress, social issues, access to and quality of medical care and behavior, contribute to racial disparity in stillbirth, the reasons for the disparity remain unclear. Knowledge gaps and recommendations for further research and interventions intended to reduce racial disparity in stillbirth are highlighted.     

Effect of maternal glucose ingestion compared with maternal water ingestion on the nonstress test

Ninety-three nonstress tests were performed on 57 nondiabetic patients at greater than 34 weeks' gestation. Maternal whole blood glucose levels were measured before beginning the nonstress test and within five minutes of the second fetal heart rate acceleration. There was a significant rise in maternal whole blood glucose levels in the maternal glucose ingestion group but not in the maternal water ingestion group. There was no significant difference in the mean time to reactivity between the two groups. These results suggest that maternal glucose ingestion does not affect time to reactivity or the incidence of reactive nonstress tests.     

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.     

死胎的预测及其高危人群的管理

死胎是各种高危因素下母体、胎儿、胎盘疾病的终末期结局。早中孕期联合母体病史、超声胎儿生长及子宫动脉多普勒血流评估、母体血清胎盘生长因子,对胎盘受损所致死胎的预测价值较高,但对足月死胎的预测价值有限。正确识别死胎的高危因素,加强高危人群的孕前及孕期管理,有效利用各种产前监护手段以及适时分娩,可降低死胎的发生率。     

The preterm nonstress test: effects of gestational age and length of study

The application of the nonstress test between 24 and 32 weeks' gestation has been limited by high rates of "false" nonreactivity in normal fetuses, by use of term criteria, and the lack of age-appropriate interpretative standards. To establish such standards, we studied 30 normal fetuses undergoing 90-minute fetal heart rate recordings at 2-week intervals from 24 to 32 weeks' gestational age. Using a specially programmed computer we quantified (1) baseline fetal heart rate, (2) incidence of 10- and 15-beat accelerations, and (3) incidence of fetal heart rate decelerations. With a criterion of three 15-beat accelerations per 30 minutes 91% of tests were reactive within 90 minutes. A criterion of three 10-beat accelerations per 30 minutes was associated with 100% reactivity within 60 minutes. Suitable interpretative criteria may be established for nonstress tests before 32 weeks' gestation by extending the testing time or by decreasing the minimum amplitude required of fetal heart rate accelerations.     

Sudden fetal death in women with well-controlled, intensively monitored gestational diabetes.

An intensive antepartum monitoring system for women with gestational diabetes mellitus was evaluated over a 5-year period. Early diagnosis and liberal treatment with insulin was concomitantly followed with non-stress testing: weekly from 28 to 34 weeks' gestation and semi-weekly thereafter. Despite maternal euglycemia and satisfactory antepartum assessment, three fetal deaths occurred within 72 hours of reassuring fetal monitoring. Additionally, 24 (7%) fetuses were delivered on the basis of a low biophysical profile score (less than 6) at term. The stillbirth rate for women with gestational diabetes was 7.7/1000, whereas the stillbirth rate for nondiabetic low-risk patients was 4.8/1000. Women with gestational diabetes continue to be in a high-risk category for antepartum fetal death, requiring intensive monitoring with consideration for timely delivery.     

The Actim Partus test to predict pre-term birth in asymptomatic high-risk women

The Actim Partus test has been shown to be a useful predictor of pre-term birth in symptomatic women, but limited research has been carried out in high-risk asymptomatic women. This is a pilot study to evaluate the use of this test as a direct comparator with the fetal fibronectin test. All asymptomatic high-risk women attending a pre-term surveillance clinic over a 9-month period, took an Actim Partus and fetal fibronectin test, between 23(+0)-24(+6) weeks' gestation. A total of 45 women were eligible. The positive and negative predictive values of the Actim Partus test for delivery at ≤ 37 weeks' gestation were 0% and 70%, respectively, compared with the fetal fibronectin test, with values of 67% and 79%, respectively. It was concluded that the Actim Partus test did not perform well as a predictor of pre-term birth in high-risk asymptomatic women.     

Rescue by birth: defective placental maturation and late fetal mortality

OBJECTIVE: To estimate the incidence and lethality of placental maturation defect, and to determine the impact of the pattern of placental dysfunction on the risk of recurrent stillbirth or maternal disease in later life. METHODS: Questionnaire and archival analysis of fetal deaths from placental dysfunction at 32-42 weeks (1975-1995 in Zurich), classified as chronic (parenchyma loss) or acute (maturation defect of the terminal chorionic villi). Population survey of 17,415 consecutive unselected singleton placentas (1994-1998 in Berlin). RESULTS: Of the 71 stillbirths, 34 were due to parenchyma loss and 37 to maturation defect. Parenchyma loss predominated in the first pregnancy (73.5% compared with 43.2%; P <.05). The risks of recurrent stillbirth and subsequent childlessness did not differ between the two groups. Eleven percent of mothers whose placenta had maturation defect had diabetes in the index pregnancy; none of the other women in the group developed diabetes over the 5-20-year observation period. In the population survey, incidence of maturation defect was 5.7%, and was associated with fetal death in 2.3% of cases. Normal placentas were associated with fetal death in 0.033%. CONCLUSION: Placental maturation defect can be a cause of fetal hypoxia. Although the risk of stillbirth is 70-fold that of a normal placenta, few affected fetuses actually die. The risk of recurrent stillbirth is tenfold above baseline and occurs mostly after 35 weeks' gestation.     

Auscultated fetal heart rate accelerations. III. Use of vibratory acoustic stimulation

The auscultated acceleration test has been proposed as a simple, inexpensive screening test for fetal health; previous studies of the auscultated acceleration test used external stimulation to elicit fetal movement. This study was conducted to explore the ability of the auscultated acceleration test to predict nonstress test results when vibratory acoustic stimulation is used to elicit fetal reactivity. After antepartum nonstress testing on 100 gravid women between 28 and 43 weeks' gestation, a 6-minute auscultated acceleration test protocol was performed with two vibratory acoustic stimulations to the maternal abdomen if no spontaneous fetal heart rate acceleration occurred. The ability of the auscultated acceleration test to predict nonstress test results after selected variables were controlled for was as follows: sensitivity, 75%; specificity, 97.6%; false-positive results, 14.3%; and false-negative results, 4.7%. Logistic regression analysis indicated that, in addition to the auscultated acceleration test, gestational age and race contributed significantly to the prediction of nonstress test results. Although specificity and the false-positive rate were improved, the use of vibratory acoustic stimulations to elicit fetal movement did not improve the validity of the auscultated acceleration test in terms of sensitivity and false-negative results over previous studies. However, the auscultated acceleration test continues to show potential as an initial screening test for fetal assessment. In addition to recommendations for further research, methodologic issues related to sampling techniques are identified.     

When Do Perinatal Deaths in Multiple Pregnancies Occur?

Perinatal mortality for multiple pregnancy remains at least 5 times the rate for singleton births. The major causes are neonatal deaths due to gross immaturity before 30 weeks' gestation, and stillbirths due to intrauterine growth retardation at all gestations, but especially after 32 weeks. Sixty four per cent of perinatal losses before 30 weeks' gestation occur before 26 weeks, highlighting the need to commence prophylactic measures earlier than usually recommended. The perinatal mortality in infants in multiple births weighing more than 2,500g is the same as that of singletons, but is 10 times this rate in multiple births weighing between 500g and 2,500g. Because the stillbirth rate in twins proceeding beyond 38 weeks' gestation is 3 times that of singleton births, elective termination of pregnancy is recommended if spontaneous labour has not occurred by this time.     

Acoustic stimulation testing

The nonstress test is the most widely employed method of fetal health assessment. The current approach is to use the OCT or biophysical profile as a means of identifying the fetus at very high risk should the nonstress test be either nonreassuring or equivocal. The acoustic stimulation test may have a predictive ability similar to that of the biophysical profile and thus may be used to complement nonstress testing as early as 28 weeks' gestation. It reliably invokes a reactive NST in those fetuses destined to demonstrate reactivity with persistence in monitoring and facilitates more rapid and efficient testing. The acoustic test may have the additional benefit of providing a screening mechanism for anomalies in which neurologic performance is suboptimal. However, because the test has not been studied on large numbers of patients and because different applications of such stimuli may elicit differing responses, its adaptation for clinical use should be cautious at the present time.     

Prospective risk of stillbirth in multiple-gestation pregnancies: a population-based analysis

OBJECTIVE: To evaluate the prospective risk of stillbirth in multiple gestations. METHODS: We conducted a retrospective analysis of birth notifications and infant mortality records relating to all multiple gestations to residents in a predefined health district. The incidence of live births and stillbirths was used to calculate the prospective risk of stillbirth at each week of gestation. RESULTS: The risk of stillbirth in multiple gestations increased from 1:3333 at 28 weeks' gestation to 1:69 at 39 or more weeks' gestation. The stillbirth risk in multiple gestations at 39 weeks surpassed that of postterm singleton pregnancies (1:526). CONCLUSION: Multiple gestations at 37-38 weeks have a risk of stillbirth equivalent to that of postterm singleton pregnancy. Because multiple gestations rarely proceed beyond 39 weeks, and because stillbirth risk increases several-fold beyond this stage, elective delivery might be justified at this gestational age.     

预防可避免死胎,重视死胎病因管理

全球死胎发生率差异较大的原因与死胎定义不一以及各地社会发展不均衡相关;以往研究发现,28周的死胎多与胎儿畸形、妊娠合并症相关;≥28周的死胎多与妊娠并发症有关,尤其胎儿生长受限;分娩过程的死胎,主要与临床监护、处置不当有关。针对不同死胎原因的管理,有望降低死胎发生率。