Trends in the cause of late fetal death, 1982-2000

BACKGROUND: Progress in reducing late fetal deaths has slowed in recent years, despite changes in intrapartum and antepartum care. OBJECTIVES: To describe recent trends in cause-specific fetal death rates. DESIGN: Retrospective cohort study. SETTING: North of England. POPULATION/SAMPLE: 3,386 late fetal deaths (> or = 28 weeks of gestation and at least 500 g), occuring between 1982 and 2000. METHODS: Data on deaths were obtained from the Northern Perinatal Mortality Survey. Data on live births were obtained from national birth registration statistics. Rate ratios (RR) and 95% confidence intervals (CI) for fetal deaths in 1991-2000 compared with 1982-1990 were calculated. MAIN OUTCOME MEASURES: Cause-specific late fetal death rates per 10,000 total births. RESULTS: Mortality in singletons declined from 51.5 per 10,000 births in 1982-1990 to 42.0 in 1991-2000 (RR 0.82, 95% CI 0.76-0.87). There was a greater decline in multiples, from 197.9 to 128.0 per 10,000 (RR 0.65, 95% CI 0.51-0.83). In singletons, the largest reductions occurred in intrapartum-related deaths, and deaths due to congenital anomalies, antepartum haemorrhage and pre-eclampsia. There was little change in the rate of unexplained antepartum death occurring at term (RR 0.97, 95% CI 0.84-1.11) or preterm (RR 0.94, 95% CI 0.82-1.07), these accounting for about half of all late fetal deaths. Unexplained antepartum deaths declined in multiple births and in singletons of birthweight < 1500 g. CONCLUSIONS: While late fetal mortality due to many specific causes has declined, unexplained antepartum death rates have remained largely unchanged. Improved identification of deaths due to growth restriction and infection, which may otherwise be classified as unexplained, is important. Further investigation of the underlying aetiologies of genuinely unexplained deaths is needed.     

Incidence of stillbirth and perinatal mortality and their associated factors among women delivering at Harare Maternity Hospital, Zimbabwe: a cross-sectional retrospective analysis

BACKGROUND: Death of an infant in utero or at birth has always been a devastating experience for the mother and of concern in clinical practice. Infant mortality remains a challenge in the care of pregnant women worldwide, but particularly for developing countries and the need to understand contributory factors is crucial for addressing appropriate perinatal health. METHODS: Using information available in obstetric records for all deliveries (17,072 births) at Harare Maternity Hospital, Zimbabwe, we conducted a cross-sectional retrospective analysis of a one-year data, (1997-1998) to assess demographic and obstetric risk factors for stillbirth and early neonatal death. We estimated risk of stillbirth and early neonatal death for each potential risk factor. RESULTS: The annual frequency of stillbirth was 56 per 1,000 total births. Women delivering stillbirths and early neonatal deaths were less likely to receive prenatal care (adjusted relative risk [RR] = 2.54; 95% confidence intervals [CI] 2.19-2.94 and RR = 2.52; 95% CI 1.63-3.91), which for combined stillbirths and early neonatal deaths increased with increasing gestational age (Hazard Ratio [HR] = 3.98, HR = 7.49 at 28 and 40 weeks of gestation, respectively). Rural residence was associated with risk of infant dying in utero, (RR = 1.33; 95% CI 1.12-1.59), and the risk of death increased with increasing gestational age (HR = 1.04, HR = 1.69, at 28 and 40 weeks of gestation, respectively). Older maternal age was associated with risk of death (HR = 1.50; 95% CI 1.21-1.84). Stillbirths were less likely to be delivered by Cesarean section (RR = 0.64; 95% CI 0.51-0.79), but more likely to be delivered as breech (RR = 4.65; 95% CI 3.88-5.57, as were early neonatal deaths (RR = 3.38; 95% CI 1.64-6.96). CONCLUSION: The frequency of stillbirth, especially macerated, is high, 27 per 1000 total births. Early prenatal care could help reduce perinatal death linking the woman to the health care system, increasing the probability that she would seek timely emergency care that would reduce the likelihood of death of her infant in utero. Improved quality of obstetric care during labor and delivery may help reduce the number of fresh stillbirths and early neonatal deaths.     

The influence of obstetric intervention on trends in twin stillbirths: United States, 1989-99.

OBJECTIVE: Although twin stillbirth rates have declined substantially over the past two decades, the contribution of changes in obstetric interventions to reducing twin stillbirths has not been quantified. METHODS: We carried out a retrospective cohort study of twin live births and stillbirths in the United States between 1989 and 1999 (n=1,102,212). Changes in the rate of stillbirth (> or =22 weeks) before and after adjustment for changes in labor induction, Cesarean delivery and sociodemographic factors were estimated through ecological logistic regression analysis. This analysis was based on aggregating data by each state within the United States. RESULTS: Between 1989 and 1999, rates of labor induction and Cesarean delivery among twin live births increased by 138% (from 5.8% to 13.8%) and 15% (from 48.3% to 55.6%), respectively. These changes were accompanied by a 43% decline in the stillbirth rate between 1989 and 1999 (from 24.4 to 13.9 per 1000 fetuses at risk). After excluding births weighing < 500 g, rates of labor induction among twins at 22-27 weeks', 28-33 weeks' and > or =34 weeks' gestation increased by 95%, 131% and 127%, respectively, between 1989 and 1999. Cesarean delivery rates also increased by 55%, 29% and 2% in these same gestational age categories. The 48% (relative risk (RR) 0.52, 95% confidence interval (CI) 0.49-0.55) decline in stillbirth rate between 1989-91 and 1997-99 was reduced to a 25% (RR 0.75, 95% CI 0.72-0.79) decline after adjustment for changes in labor induction and Cesarean delivery. The decline in the rate of twin stillbirths was larger at later gestational ages (at > or =32 and > or =34 weeks) where the largest absolute increases in labor induction rates were observed. CONCLUSIONS: The use of Cesarean delivery and especially labor induction for twin pregnancies has increased substantially in the United States over the last decade and these changes have been associated with a large decline in the rate of stillbirth among twins.     

Outcomes of planned home births in Washington State: 1989-1996

OBJECTIVE: To determine whether there was a difference between planned home births and planned hospital births in Washington State with regard to certain adverse infant outcomes (neonatal death, low Apgar score, need for ventilator support) and maternal outcomes (prolonged labor, postpartum bleeding). METHODS: We examined birth registry information from Washington State during 1989-1996 on uncomplicated singleton pregnancies of at least 34 weeks' gestation that either were delivered at home by a health professional (N = 5854) or were transferred to medical facilities after attempted delivery at home (N = 279). These intended home births were compared with births of singletons planned to be born in hospitals (N = 10,593) during the same years. RESULTS: Infants of planned home deliveries were at increased risk of neonatal death (adjusted relative risk [RR] 1.99, 95% confidence interval [CI] 1.06, 3.73), and Apgar score no higher than 3 at 5 minutes (RR 2.31, 95% CI 1.29, 4.16). These same relationships remained when the analysis was restricted to pregnancies of at least 37 weeks' gestation. Among nulliparous women only, these deliveries also were associated with an increased risk of prolonged labor (RR 1.73, 95% CI 1.28, 2.34) and postpartum bleeding (RR 2.76, 95% CI 1.74, 4.36). CONCLUSION: This study suggests that planned home births in Washington State during 1989-1996 had greater infant and maternal risks than did hospital births.     

Fetal deaths in the United States. Influence of high-risk conditions and implications for management

OBJECTIVE: To estimate the effect of specific maternal-fetal high-risk conditions on the risk and timing of fetal death. METHODS: This study examined 10,614,679 non-anomalous singleton pregnancies delivering at or beyond 24 weeks' gestation, derived from the U.S. linked birth/infant death data sets, 1995-1997. Fetal death rates for pregnancies at low risk were compared with pregnancies complicated by chronic hypertension, gestational hypertensive disorders, diabetes, small for gestational age infants, and abruption. Adjusted relative risks as well as population-attributable risks for fetal death were derived by gestational age for each high-risk condition compared with low-risk pregnancies. RESULTS: The fetal death rate for low-risk pregnancies was 1.6 per 1000 births. Adjusted relative risk for fetal death was 9.2 (95% confidence interval [CI] 8.8, 9.7) for abruption, 7.0 (95% CI 6.8, 7.2) for small for gestational age infants, 1.4 (95% CI 1.3, 1.5) for gestational hypertensive disorders, 2.7 (95% CI 2.4, 3.0) for chronic hypertension, and 2.5 (95% CI 2.3, 2.7) for diabetes. Fetal death rates were lowest between 38 and 41 weeks. The fetal death rate (per 1000 births) for these high-risk conditions was 61.4, 9.6, 3.5, 7.6, and 3.9, respectively. Almost two thirds of fetal deaths were attributable to the pregnancy complications examined. CONCLUSION: High-risk conditions in pregnancy are associated with an increased risk for fetal death, particularly in the third trimester. Delivery should be considered at 38 weeks, but no later than 41 weeks, for these pregnancies.     

The risk of perinatal mortality with each week of expectant management in obese pregnancies

Introduction: The risk of stillbirth associated with maternal obesity increases with gestational age; however, it is unclear if earlier delivery reduces the overall perinatal mortality rate. Our objective was to compare the risk of perinatal mortality associated with each additional week of expectant management to that of immediate delivery.

Methods: This was a retrospective cohort study of singleton non-anomalous births in Texas between 2006 and 2011. Analyses were stratified based on maternal pre-pregnancy BMI class. For each BMI class, we calculated the rate of neonatal death and stillbirth at each week of gestation from 34 to 41 weeks. A composite risk of perinatal mortality associated with 1 week of expectant management was estimated combining the stillbirth rate of the current week and the neonatal death rate of the following week. This was compared with the rate of neonatal death of the current week.

Results: After all exclusions, 2,149,771 births remained for analysis. In the normal weight group, stillbirth risk increased from 0.8 per 10,000 births at 34 weeks to 5.7 per 10,000 births at 42 weeks, whereas the neonatal death risk decreased from 76.5 per 10,000 births at 34 weeks to 30.4 per 10,000 births at 42 weeks, there were no differences between expectant management and delivery for any gestational week. In the obese group, stillbirth risk increased from 1.8 per 10,000 births at 34 weeks to 10.5 per 10,000 births at 42 weeks, whereas the neonatal death risk decreased from 67.7 per 10,000 births at 34 weeks to 26.2 per 10,000 births at 42 weeks, the perinatal mortality risk favored delivery at 39 weeks (RR: 1.17; 99% CI: 1.01–1.36) and not thereafter. In contrast, in the morbidly obese group, stillbirth risk increased from 8.8 per 10,000 births at 34 weeks to 83.7 per 10,000 births at 42 weeks, whereas the neonatal death risk decreased from 63.6 per 10,000 births at 34 weeks to 15.5 per 10,000 births at 42 weeks, the perinatal mortality risk favored delivery from 38 weeks (RR: 1.53; 99% CI: 1.16–2.02) through 41 weeks (RR: 5.39; 99% CI: 1.83–15.88).

Conclusion: The findings reported here suggest that delivery by 38 weeks in gestation minimizes perinatal mortality in pregnancies complicated by maternal morbid obesity.     

The impact of prenatal care on neonatal deaths in the presence and absence of antenatal high-risk conditions

OBJECTIVE: The purpose of this study was to determine the association between prenatal care in the United States and the neonatal death rate in the presence and absence of antenatal high-risk conditions. STUDY DESIGN: Data were derived from the national perinatal mortality data sets for the years 1995 through 1997, which were provided by the National Center for Health Statistics. Analyses were restricted to singleton live births that occurred after 23 completed weeks of gestation. Multivariable logistic regression analyses were used to adjust for the presence or absence of various antenatal high-risk conditions, maternal age, gestational age at delivery, and birth weight. RESULTS: Of 10,530,608 singleton live births, 18,339 (1.7/1000 births) resulted in neonatal death. Neonatal death rates (per 1000 live births) were higher for African American infants compared with white infants in the presence (2.7 vs 1.5, respectively) and absence (10.7 vs 7.9, respectively) of prenatal care. Lack of prenatal care was associated with an increase in neonatal deaths, which was greater for infants born at > or =36 weeks of gestation (relative risk, 2.1; 95% CI, 1.8, 2.4). Lack of prenatal care was also associated with increased neonatal death rates in the presence of preterm premature rupture of the membranes (relative risk, 1.3; 95% CI, 1.1, 1.5), placenta previa (relative risk, 1.9; 95% CI, 1.2, 2.9), fetal growth restriction (relative risk, 1.7; 95% CI, 1.2, 1.6), and postterm pregnancy (relative risk, 1.4; 95% CI, 1.0, 2.9). CONCLUSION: In the United States, prenatal care is associated with fewer neonatal deaths in black and white infants. This beneficial effect was more pronounced for births that occurred at > or =36 weeks of gestation and in the presence of preterm premature rupture of the membranes, placenta previa, fetal growth restriction, and postterm pregnancy.     

The influence of obstetric intervention on trends in twin stillbirths: United States, 1989–99

Objective: Although twin stillbirth rates have declined substantially over the past two decades, the contribution of changes in obstetric interventions to reducing twin stillbirths has not been quantified.

Methods: We carried out a retrospective cohort study of twin live births and stillbirths in the United States between 1989 and 1999 (n?=?1?102?212). Changes in the rate of stillbirth (???22 weeks) before and after adjustment for changes in labor induction, Cesarean delivery and sociodemographic factors were estimated through ecological logistic regression analysis. This analysis was based on aggregating data by each state within the United States.

Results: Between 1989 and 1999, rates of labor induction and Cesarean delivery among twin live births increased by 138% (from 5.8% to 13.8%) and 15% (from 48.3% to 55.6%), respectively. These changes were accompanied by a 43% decline in the stillbirth rate between 1989 and 1999 (from 24.4 to 13.9 per 1000 fetuses at risk). After excluding births weighing <?500?g, rates of labor induction among twins at 22–27 weeks', 28–33 weeks' and ??34 weeks' gestation increased by 95%, 131% and 127%, respectively, between 1989 and 1999. Cesarean delivery rates also increased by 55%, 29% and 2% in these same gestational age categories. The 48% (relative risk (RR) 0.52, 95% confidence interval (CI) 0.49–0.55) decline in stillbirth rate between 1989–91 and 1997–99 was reduced to a 25% (RR 0.75, 95% CI 0.72–0.79) decline after adjustment for changes in labor induction and Cesarean delivery. The decline in the rate of twin stillbirths was larger at later gestational ages (at ??32 and ??34 weeks) where the largest absolute increases in labor induction rates were observed.

Conclusions: The use of Cesarean delivery and especially labor induction for twin pregnancies has increased substantially in the United States over the last decade and these changes have been associated with a large decline in the rate of stillbirth among twins.     

Effect of labor on infant morbidity and mortality with preterm premature rupture of membranes: United States population-based study

OBJECTIVE: To evaluate whether labor, in the setting of premature rupture of membranes (PROM), affects infant morbidity and mortality rates. METHODS: We derived data for this population-based cohort study from the United States national linked birth infant death data sets, comprised of singleton live births delivered between 1995 and 1997. We included women (n = 34,594) who had preterm PROM more than 12 hours and delivered between 23 and 32 weeks' gestation. Birth records were used to determine whether delivery occurred with or without labor. Infants with birth weights below the tenth percentile for gestational age were classified as small for gestational age (SGA) on the basis of a nomogram of all singleton births in the United States between 1995 and 1997. Primary outcomes were early neonatal (0-6 days), late neonatal (7-27 days), postneonatal (28-365 days), and infant death (0-365 days). Secondary outcomes included respiratory distress syndrome (RDS), assisted ventilation, and neonatal seizures. Risks of infant mortality and morbidity from labor were examined separately for SGA and non-SGA infants. RESULTS: Overall rates were infant death 11.6%, RDS 15.1%, assisted ventilation 25.9%, and neonatal seizure 0.2%. Labor was associated with higher incidence of early neonatal death in SGA infants (adjusted relative risk [RR] 1.24, 95% confidence interval [CI] 1.11, 1.38) but had no effect on other outcomes. Among non-SGA infants, labor had no effect on infant death but was associated with higher rates of RDS (RR 1.15, 95% CI 1.08, 1.22) and assisted ventilation (RR 1.16, 95% CI 1.08, 1.24). CONCLUSION: Although labor was associated with a slightly higher mortality rate in SGA infants and slightly more respiratory morbidity in non-SGA infants, recommendations regarding clinical treatment should await future clinical trials.     

Cesarean delivery or vaginal birth: a survey of patient and clinician thresholds

OBJECTIVE: To estimate what level of additional fetal risk women and their caregivers in late pregnancy considered acceptable to avoid a cesarean and achieve a vaginal birth. METHODS: Six hundred women in late pregnancy and 294 obstetric consultants, registrars, midwives, and medical students were recruited to the study. With the assistance of a visual probability aid representing 10,000 births, they were asked to consider what level of fetal risk of death or serious disability they would consider acceptable to avoid cesarean and achieve vaginal birth. RESULTS: The median level of fetal risk deemed acceptable to achieve a vaginal birth for pregnant women was 10 per 10,000 births (95% confidence interval [CI] 10-13 per 10,000), although the range of responses was wide (1-5,000 per 10,000). Among staff, the median level of acceptable fetal risk was 13 per 10,000 births (95% CI 10-20 per 10,000). Women participating in lower intervention models of care, such as the birth center or team midwifery, were more tolerant of fetal risk (odds ratios [ORs] 2.1, 95% CI 1.6-2.9 and 1.5, 95% CI 1.0-2.3, for accepting a fetal risk of 20 per 10,000 or greater), whereas women with a complicated pregnancy were less tolerant of fetal risk (OR 0.7, 95% CI 0.5-0.9). CONCLUSION: Pregnant women and their caregivers have a low tolerance for fetal risk associated with vaginal birth. This study demonstrates the difficulty of minimizing obstetric intervention rates in the face of high expectations for fetal outcome. Obstetric and demographic factors were found to significantly impact the "acceptable fetal risk" threshold, which highlights the importance of individualized counseling regarding mode of birth. LEVEL OF EVIDENCE: III.     

The value of quantitative ultrasound tissue characterization of the cervix and rapid fetal fibronectin in predicting preterm delivery

OBJECTIVE: To evaluate clinical risk factors, cervical fetal fibronectin (fFN), cervical length, and mean gray value assessment in predicting of preterm delivery (PTD) in patients with signs and/or symptoms of preterm labor (PTL). STUDY DESIGN: One hundred and seventeen women with PTL between 24 and 34 weeks of gestation were included. Cervical swabs were tested for fFN using the rapid fFN assay. When 2-dimensional transvaginal ultrasound measurement of cervical length was completed, a region of interest (ROI) of constant size was defined in the midsection of the posterior wall, and the tissue-specific gray scale was determined. The end point were PTDs at <34 and <37 weeks of gestation. RESULTS: In univariate analysis, the three strongest predictors of spontaneous preterm birth <34 weeks were positive fFN (relative risk [RR] 8.9; 95% confidence interval [CI] 2.6-30.1), cervical length < or =2.5 cm (RR 6.9; 95% CI 1.6-29.7), and a low mean gray value of < or =5.97 (RR 7.9; 95% CI 2.3-27.2). Predictors significantly associated with spontaneous PTD at less than 37 weeks of gestation included previous PTD in multiparas (RR 3.9; 95% CI 1.6-9.5), positive fFN (RR 7.6; 95% CI 3.8-15.3), cervical length < or =2.5 cm (RR 2.6; 95% CI 1.4-5.1) and a low gray scale value of < or =6.54 (RR 4.5; 95% CI 2.3-8.9). In the final regression models used to predict spontaneous PTD <34 weeks and <37 weeks of gestation, both a positive fetal fibronectin (odds ratio [OR] 13.4; 95% CI, 2.5-72.1, P=0.003 vs. OR, 17.3; 95% CI 4.9-61.8, P<0.001) and a low gray scale value (OR 6.3 95% CI 1.3-29.4, P=0.02 vs. OR, 7.1; 95% CI 2-25.2, P=0.003) remained powerful predictors. The RRs of spontaneous PTD <37 weeks has been analyzed by a combination of these significant parameters. Low mean gray value < or =6.54 and negative fFN had a 10.3-fold (95% CI 2-74.5) increased risk of spontaneous preterm birth at <37 weeks. Combination of positive fFN and normal gray level (>6.54), had a higher increase risk of PTD (RR 18.1; 95% CI 4.4-76.7). When both factors were positive, the RR increases to 24.8 (95% CI 6.2-98.7). CONCLUSIONS: Combined use of rapid fFN and cervical gray value analysis improves the diagnostic efficiency and allows identification of women at risk for preterm delivery and in need for further prophylactic/therapeutic intervention.     

Racial disparity in meconium-stained amniotic fluid and meconium aspiration syndrome in the United States, 1989-2000

OBJECTIVE: To estimate the prevalence of meconium-stained amniotic fluid and meconium aspiration syndrome, as well as the differences in case fatality from meconium aspiration syndrome, between non-Hispanic black and non-Hispanic white infants. METHODS: We studied non-Hispanic black and non-Hispanic white live births with weights greater than 2.5 kg and gestational ages greater than 35 weeks, using the linked US birth and infant death cohorts for three periods: 1989-1991, 1995-1997, and 1998-2000. We used logistic regression to estimate the risks of meconium-stained amniotic fluid and meconium aspiration syndrome and to estimate the case fatality of meconium aspiration syndrome by maternal race, birth weight, period, and pregnancy complications. RESULTS: Risk of meconium-stained amniotic fluid was 80% higher in non-Hispanic blacks when compared with non-Hispanic whites (birth weight-adjusted odds ratio [OR], 1.81, 95% confidence interval [CI] 1.80, 1.82). The prevalence of pregnancy complications did not explain this racial disparity. Risk of meconium aspiration syndrome in non-Hispanic blacks was 67% higher when compared with non-Hispanic whites (birth weight-adjusted OR 1.67, 95% CI 1.64, 1.70). The case fatality rate of meconium aspiration syndrome was similar between non-Hispanic blacks and non-Hispanic whites in the three periods, with rates of 15.5, 15.2, and 11.2 per 1000 in non-Hispanic blacks and 13.5, 11.2, and 10.1 per 1000 in non-Hispanic whites in 1989-1991, 1995-1997, and 1998-2000, respectively. CONCLUSION: Our results suggest that when compared with non-Hispanic whites, non-Hispanic blacks are at significantly greater risk for meconium-stained amniotic fluid and meconium aspiration syndrome but not for meconium aspiration syndrome case fatality.     

Birth weight and fetal death in the United States: the effect of maternal diabetes during pregnancy

OBJECTIVE: Our purpose was to evaluate the association between birth weight (BW) and fetal death (FD) among pregnant nondiabetic and diabetic patients. STUDY DESIGN: This was a retrospective cohort study using data for singleton births delivered between 1995 and 1997 in the United States (n = 10, 733, 983). Analysis was restricted to births that occurred at > or =20 completed weeks. FD rates among nondiabetic and diabetic patients (n = 271, 691) were determined for different 250-g BW categories. Adjusted relative risk (RR) and 95% CI for FD among diabetic compared with nondiabetic patients were derived through multivariable logistic regression models after potential confounders were controlled. RESULTS: Overall FD rates for nondiabetic and diabetic patients were 4.0 and 5.9 per 1,000 births, respectively, with adjusted RR of 2.0 (95% CI 1.8-2.2). Maternal diabetes was associated with increased FD rate for all BW categories after 1250 g. CONCLUSION: The FD rate is increased when birth weight is > or =4250 g in nondiabetic patients and > or =4000 g in diabetic patients.     

Adverse perinatal outcomes among interracial couples in the United States

OBJECTIVE: We examined the association between parental race and stillbirth and adverse perinatal and infant outcomes. METHODS: We conducted a retrospective cohort analysis using the 1995-2001 linked birth and infant death files that are composed of live births and fetal and infant deaths in the United States. The study included singleton births delivered at 20 or more weeks of gestation with a fetus weighing 500 g or more (N = 21,005,786). Parental race was categorized as mother white-father white, mother white-father black, mother black-father white, and mother black-father black. Multivariable logistic regression analysis was performed to examine the association between parental race and risks of stillbirth (at > or = 20 weeks), small for gestational age (defined as birth weight < 5th and < 10th percentile for gestational age), and early neonatal (< 7 days), late neonatal (7-27 days), and postneonatal (28-364 days) mortality. All analyses were adjusted for the confounding effects of maternal age, education, trimester at which prenatal care began, parity, marital status, and smoking during pregnancy. RESULTS: Although risks varied across parental race categories, stillbirth was associated with a higher-than-expected risk for interracial couples: mother white-father black, relative risk (RR) 1.17 (95% confidence interval [CI] 1.10-1.26) and mother black-father white, RR 1.37 (95% CI 1.21-1.54) compared with mother white-father white parents. The RR for stillbirth was even higher among mother black-father black parents (RR 1.67, 95% CI 1.62-1.72). The overall patterns of association for small for gestational age births (< 5th and < 10th percentile) and early neonatal mortality were similar to those seen for stillbirth. CONCLUSION: There is an increased risk of adverse perinatal outcomes for interracial couples, including stillbirth, small for gestational age infants, and neonatal mortality. LEVEL OF EVIDENCE: II-2.     

Perinatal mortality in first- and second-born twins in the United States

OBJECTIVE: To evaluate the prevailing mortality paradox that second-born twins are at higher risk of perinatal mortality than first-born twins. METHODS: We used the 1995-1997 United States "matched multiple birth" data files assembled by the National Center for Health Statistics, for analysis of risk of perinatal mortality in first- and second-born twins (293788 fetuses). Perinatal mortality was defined to include stillbirths after 20 weeks of gestation and neonatal deaths (deaths within the first 28 days). Gestational age-specific risk of perinatal mortality (per 1000 total births), stillbirth (per 1000 total births), and neonatal mortality (per 1000 livebirths) by order of twin birth were based on the fetuses-at-risk approach. Associations between order of birth and mortality indices were evaluated by fitting multivariable logistic regression models based on the method of generalized estimating equations. These models were adjusted for several potential confounding factors. RESULTS: Perinatal mortality was 37% higher in second-born (26.1 per 1000 total births) than in first-born (20.3 per 1000 total births) twins (adjusted relative risk [RR] 1.37; 95% confidence interval [CI] 1.32, 1.42). The increased risk of perinatal mortality in second-born twins was chiefly driven by a 2.46-fold (95% CI 2.29, 2.63) increase in the number of stillbirths. However, the risk of neonatal mortality was very similar between first- and second-born twins (RR 0.99, 95% CI 0.95, 1.04). CONCLUSIONS: The increased risk of perinatal death in second-born twins is driven chiefly by increased rates of stillborn second twins. Thus, the increased mortality in second-born over first-born twins probably is an artifact of mortality comparisons.     

Maternal age and risk of fetal death in singleton gestations: USA, 1995-2000.

OBJECTIVE: To determine the magnitude of risk for fetal death among singleton pregnancies in relation to maternal age, and to compare the risks with other common indications for fetal testing. STUDY DESIGN: We performed a retrospective cohort analysis of singleton births delivered between 1995 and 2000 using the US linked birth/infant death data. Gestational age at < 24 weeks and fetuses with anomalies were excluded. Fetal death rates at > or = 24 and > or = 32 weeks were calculated among women aged 15-19, 20-24, 25-29, 30-34, 35-39, 40-44 and 45-49 years, as well as for other common indications for testing: chronic and pregnancy-induced hypertension, diabetes and small-for-gestational age (SGA). The association between maternal age and fetal deaths was derived after adjusting for potential confounders through multivariable logistic regression models. Relative risks (RR) and 95% confidence intervals (CI) were derived from these models after adjusting for the effects of gravidity, race, marital status, prenatal care, education, smoking and placental abruption. RESULTS: Among the 21,610,873 singleton births delivered at > or = 24 weeks, fetal deaths occurred in 58,580 (2.7 per 1000). Births to young (15-19 years) and older (> or = 35 years) women comprised 12.6% and 11.4%, respectively. Compared with women aged 20-24 years, young women did not experience an increased risk of fetal death. However, increasing rates of fetal death at > or = 24 and at > or = 32 weeks were seen with increasing maternal age. The RR for fetal death at > or = 24 and at > or = 32 weeks among women 35-39 years were 1.21 and 1.31, respectively, while the RRs were 1.62 and 1.67 among women aged 40-44 years. Women 45-49 years were 2.40-fold (95% CI 1.77, 3.27) and 2.38-fold (95% CI 1.64, 3.46) as likely to deliver a stillborn fetus at > or = 24 weeks and > or = 32 weeks, respectively. RRs for fetal death at > or = 24 and > or = 32 weeks for hypertensive disease, diabetes, and SGA ranged between 1.46 and 4.95. CONCLUSION: Fetal deaths are increased among older women (> or = 35 years). Fetal testing in women of advanced maternal age may be beneficial.     

Determinants of unexplained antepartum fetal deaths

OBJECTIVE: To assess fetal, maternal, and pregnancy-related determinants of unexplained antepartum fetal death. METHODS: We conducted a hospital-based cohort study of 84,294 births weighing 500 g or more from 1961-1974 and 1978-1996. Unexplained fetal deaths were defined as fetal deaths occurring before labor without evidence of significant fetal, maternal, or placental pathology. RESULTS: One hundred ninety-six unexplained antepartum fetal deaths accounted for 27.2% of 721 total fetal deaths. Two thirds of the unexplained fetal deaths occurred after 35 weeks' gestation. The following factors were independently associated with unexplained fetal death: maternal prepregnancy weight greater than 68 kg (adjusted odds ratio [OR] 2.9; 95% confidence interval [CI] 1.85, 4.68), birth weight ratio (defined as ratio of birth weight to mean weight for gestational age) between 0.75 and 0.85 (OR 2.77; 95% CI 1.48, 5.18) or over 1.15 (OR 2.36; 95% CI 1.26, 4.44), fewer than four antenatal visits in women whose fetuses died at 37 weeks or later (OR 2.21; 95% CI 1.08, 4.52), primiparity (OR 1.74; 95% CI 1.26, 2.40), parity of three or more (OR 2.01; 95% CI 1.26, 3.20), low socioeconomic status (OR 1.59; 95% CI 1.14, 2.22), cord loops (OR 1.75; 95% CI 1.04, 2.97) and, for the 1978-1996 period only, maternal age 40 years or more (OR 3.69; 95% CI 1.28, 10.58). Trimester of first antenatal visit, low maternal weight, postdate pregnancy, fetal-to-placental weight ratio, fetal sex, previous fetal death, previous abortion, cigarette smoking, and alcohol use were not significantly associated with unexplained fetal death. CONCLUSION: In this study, we identified several factors associated with an increased risk of unexplained fetal death.     

Risk factors and outcomes associated with a short umbilical cord

OBJECTIVE: To identify risk factors and outcomes associated with a short umbilical cord. METHODS: We conducted a population-based case-control study using linked Washington State birth certificate-hospital discharge data for singleton live births from 1987 to 1998 to assess the association between maternal, pregnancy, delivery, and infant characteristics and short umbilical cord. Cases (n = 3565) were infants diagnosed with a short umbilical cord. Controls (n = 14260) were randomly selected from among births without a diagnosis of short umbilical cord. RESULTS: Case mothers were less likely to be overweight (body mass index 25 or more, odds ratio [OR] 0.7; 95% confidence interval [CI] 0.6, 0.8) and more likely to be primiparous (OR 1.4; 95% CI 1.3, 1.6). Case infants were more likely to be female (OR 1.3; 95% CI 1.2, 1.4), have a congenital malformation (OR 1.6; 95% CI 1.4, 1.8), and be small for their gestational age (risk ratio [RR] 1.6; 95% CI 1.4, 1.9). A short cord was associated with increased risk for maternal labor and delivery complications, including retained placenta (RR 1.6; 95% CI 1.2, 2.3) and operative vaginal delivery (RR 1.4; 95% CI 1.3, 1.5). Adverse fetal and infant outcomes in cases included fetal distress (RR 1.8; 95% CI 1.6, 2.1) and death within the first year of life among term infants (RR 2.4; 95% CI 1.2, 4.6). CONCLUSION: Modifiable risk factors associated with the development of a short cord were not identified. Case mothers and infants are more likely to experience labor and delivery complications. Term case infants had a 2-fold increased risk of death, which suggests closer postpartum monitoring of these infants.     

A randomized comparison of oral mifepristone to intravenous oxytocin for labor induction in women with prelabor rupture of membranes beyond 36 weeks' gestation

OBJECTIVE: This study was undertaken to compare the use of oral mifepristone with intravenous oxytocin for labor induction in women with prelabor rupture of membranes (PROM) at 36 weeks' or greater gestational age. STUDY DESIGN: Sixty-five women with spontaneous PROM were randomly assigned to receive orally administered mifepristone or oxytocin infusion. Two hundred milligrams of mifepristone was administered, and subjects were observed for 18 hours, or intravenous oxytocin was administered. RESULTS: Thirty-three women received mifepristone and 32 received oxytocin. The average interval from start of induction to delivery was 1194.1 +/- 568.7 minutes for mifepristone-treated subjects and 770.8 +/- 519.9 minutes for oxytocin-treated subjects ( P = .001, log-transformed data). Of 33 mifepristone-treated subjects and 32 oxytocin-treated subjects, 25 (78.1%) and 17 (51.5%), respectively, achieved successful induction (defined as vaginal delivery within 24 hours) (relative risk [RR] 0.66, 95% CI 0.45-0.96, P = .01). There was more fetal distress in the mifepristone-treated group (9 vs 2, RR 4.36, 95% CI 1.02-18.66, P = .02), and a trend toward more cesarean births (7 vs 3, RR 2.26, 95% CI 0.64-7.99, P = .19). Eleven infants of mifepristone-treated women (33.3%) and 3 infants of oxytocin-treated women (9.4%) were admitted to the neonatal intensive care unit (RR 3.56, 95% CI 1.09-11.58, P = .02). CONCLUSION: Oral mifepristone administration 18 hours before oxytocin infusion did not improve labor stimulation in women with PROM near term, and was associated with more adverse fetal outcomes.     

Trends in twin neonatal mortality rates in the United States, 1989 through 1999: influence of birth registration and obstetric intervention

OBJECTIVE: We sought to evaluate the contributions of changes in birth registration, labor induction, and cesarean delivery on trends in twin neonatal mortality rates. STUDY DESIGN: We conducted a population-based, retrospective cohort study of twin live births, using linked birth-infant death data in the United States (1989-1999). Relative risks and 95% confidence intervals that quantified changes in neonatal (0-27 days) mortality rates were derived from ecologic logistic regression models that were fit after aggregation of the data by each state in the United States. RESULTS: The frequency of live born twins who weighed <500 g increased 72%, from 0.7% in 1989 to 1.2% in 1999, of live born twins who weighed 500 to 749 g and 750 to 999 g increased by 55% and 28%, respectively, between 1989 and 1999. Preterm birth rates increased by 19%, from 46.2% in 1989 to 57.2% in 1999. The rate of labor induction increased from 5.8% to 13.9%, and the cesarean delivery rate increased from 49.8% to 56.3%. Between 1989 to 1991 and 1997 to 1999, the crude neonatal mortality rates among twins who weighed >or=500 g declined by 37% (95% CI, 35%-40%) from 21.5 to 13.6 per 1000 twin live births. Adjustments for preterm labor induction, preterm cesarean delivery, term labor induction, term cesarean delivery, and sociodemographic factors had little influence on neonatal mortality rate trends. CONCLUSION: Increases in preterm birth because of obstetric intervention among twins have not led to increases in twin neonatal mortality rates in the United States.