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.     

Maternal risk factors for cause-specific stillbirth and neonatal death

BACKGROUND: To study specific effects of four maternal risk factors: age, parity, educational level, smoking, for specific causes of stillbirth and neonatal death according to a previously described hierarchic classification. METHODS: The study is based on 9,785 stillbirths or neonatal deaths among infants born in Sweden, 1983-1995 (n=1,412,754) and identified with various Swedish health registers. Statistical analysis is performed using Mantel-Haenszel analysis. RESULTS: Some risk factors, known from the literature, were confirmed and could be quantified. In addition, high parity was shown to increase the risk for death associated with multiple births (OR=2.49, 95% CI 2.07-3.01) and low educational level seems to be protective for such death (OR=0.75, 95% CI 0.60-0.93). If the infant is SGA, the risk for death is higher at high than at low parity (1.70, 95% CI 1.19-2.43, and 1.0, 95% CI 1.06-1.15, respectively). Maternal smoking seems to aggravate the placental abruption because the death risk in the presence of abruption increases when the mother smoked (OR = 1.74, 95% CI 45-2.08). CONCLUSIONS: The study shows that the groups of the classification system used (NICE) differ in their association with known risk factors for stillbirth and neonatal deaths and an analysis based on specific causes of death can therefore unravel risk factors hidden when total mortality is used. The computerized method of classification and the cause-of-death classification developed by us is clearly useful for such analyses which requires large materials.     

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.     

Pre-pregnancy weight and the risk of stillbirth and neonatal death

OBJECTIVE: To evaluate the association between maternal pre-pregnancy body mass index (BMI) and the risk of stillbirth and neonatal death and to study the causes of death among the children. DESIGN: Cohort study of pregnant women receiving routine antenatal care in Aarhus, Denmark. SETTING: Aarhus University Hospital, Denmark, 1989-1996. POPULATION: A total of 24,505 singleton pregnancies (112 stillbirths, 75 neonatal deaths) were included in the analyses. METHODS: Information on maternal pre-pregnancy weight, height, lifestyle factors and obstetric risk factors were obtained from self-administered questionnaires and hospital files. We classified the population according to pre-pregnancy BMI as underweight (BMI <18.5 kg/m(2)), normal weight (BMI 18.5-24.9 kg/m(2)), overweight (BMI 25-29.9 kg/m(2)) and obese (BMI 30.0 kg/m(2) or more). MAIN OUTCOME MEASURES: Stillbirth and neonatal death and causes of death. RESULTS: Maternal obesity was associated with a more than doubled risk of stillbirth (odds ratio = 2.8, 95% confidence interval [CI]: 1.5-5.3) and neonatal death (odds ratio = 2.6, 95% CI: 1.2-5.8) compared with women of normal weight. No statistically significantly increased risk of stillbirth or neonatal death was found among underweight or overweight women. Adjustment for maternal cigarette smoking, alcohol and caffeine intake, maternal age, height, parity, gender of the child, years of schooling, working status and cohabitation with partner did not change the conclusions, nor did exclusion of women with hypertensive disorders or diabetes mellitus. No single cause of death explained the higher mortality in children of obese women, but more stillbirths were caused by unexplained intrauterine death and fetoplacental dysfunction among obese women compared with normal weight women. CONCLUSION: Maternal obesity more than doubled the risk of stillbirth and neonatal death in our study. The present and other studies linking maternal obesity to an increased risk of severe adverse pregnancy outcomes emphasise the need for public interventions to prevent obesity in young women.     

Early mortality in twin pregnancies complicated by premature rupture of membranes in the United States.

There is little information on mortality among multiple gestations complicated by premature rupture of membranes (PROM). In this study, we estimated the occurrence of the components of early mortality (stillbirth, neonatal and infant mortality) among twin pregnancies using the generalised estimating equation framework to account for intra-cluster correlations. Using the population-attributable risk, we also computed the level of excess mortality that could be averted by preventing PROM. Our findings reveal that the likelihood of stillbirth (odds ratio (OR) = 1.88; 95% confidence interval (CI)=1.66-2.13), neonatal mortality (OR=3.45; 95% CI=3.18-3.74) and infant mortality (OR=3.26; 95% CI=3.03-3.50) was significantly higher among twin pregnancies exposed to PROM. Approximately 6% of all stillbirths, 15% of neonatal mortality and 14% of infant mortality among twins in the United States are attributable to PROM. We conclude that PROM is associated with an increased level of early mortality among twins.     

Pregnancy-induced hypertension is associated with lower infant mortality in preterm singletons

OBJECTIVE: To assess the association between pregnancy-induced hypertension (PIH) and infant mortality. DESIGN: Retrospective cohort study. SETTING: Birth and infant death registration dataset of the USA. POPULATION: A total of 17,432,987 eligible, liveborn singleton births in 1995-2000. METHODS: Multivariate logistic regression was applied to evaluate the association between PIH and infant mortality, with adjustment of potential confounders. MAIN OUTCOME MEASURES: Infant death (0-364 days) and its three components: early neonatal death (0-6 days), late neonatal death (7-27 days), and postneonatal death (28-364 days). RESULTS: There was a significant reduction in infant mortality associated with PIH in early preterm infants (OR = 0.59, 95% CI: 0.56-0.63) and in late preterm infants (OR = 0.80, 95% CI: 0.73-0.87), but a significant increase in term infants (OR = 1.08, 95% CI: 1.02-1.14). Both in early preterm and late preterm births, early neonatal mortality (OR = 0.38, 95% CI: 0.34-0.42; OR = 0.68, 95% CI: 0.61-0.77) and late neonatal mortality (OR = 0.59, 95% CI: 0.50-0.70; OR = 0.76, 95% CI: 0.61-0.96) were decreased in infants born to mothers with PIH compared with those born to mothers with normal blood pressure. The PIH-associated reduction in neonatal mortality among preterm singletons was stronger in small-for-gestational-age infants than in normal growth infants and stronger in infants born to nulliparous women than in those born to multiparous women. CONCLUSIONS: PIH is associated with lower risk of infant death in preterm births but higher risk in term births.     

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.     

Second-trimester maternal serum alpha-fetoprotein and risk of adverse pregnancy outcome(1)

OBJECTIVE: To determine the risk of adverse pregnancy outcome by maternal serum alpha-fetoprotein (MSAFP) level. METHODS: We followed 77,149 pregnant women and their infants from MSAFP screening in the 15th to 20th week of gestation until 1 year after birth. Information on pregnancy outcome was obtained from national registries. The relative risks (RRs) and 95% confidence intervals (CIs) for adverse pregnancy outcome were estimated according to the level of MSAFP, with adjustment for confounders. RESULTS: A total of 638 pregnancies resulted in spontaneous abortion, 289 in stillbirth, and 437 in infant death. Compared with women with MSAFP levels at 0.75-1.24 multiples of the median (MoM), those with MSAFP levels greater than or equal to 2.5 MoM had an increased risk of spontaneous abortion (RR 12.5; 95% CI 9.7, 16.1), preterm birth (RR 4.8; 95% CI 4.1, 5.5), small for gestational age (RR 2.8; 95% CI 2.4, 3.2), low birth weight (RR 5.8; 95% CI 5.0, 6.6), and infant death (RR 1.9; 95% CI 1.2, 2.8). Women with MSAFP levels below 0.25 MoM had an increased risk of spontaneous abortion (RR 15.1; 95% CI 9.3, 24.8), preterm birth (RR 2.2; 95% CI 1.3, 3.8), and stillbirth (RR 4.0; 95% CI 1.0, 16.0); those with levels less than 0.5 MoM had an increased risk of infant death (RR 1.9; 95% CI 1.2, 3.0). The increased risk of infant death remained after the subtraction of recognized conditions associated with extreme MSAFP values. CONCLUSION: Pregnant women with extreme MSAFP values in the second trimester have an increased risk of fetal and infant deaths. Obstet Gynecol 2001;97:277-82.     

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.     

Is a poor pregnancy outcome related to young maternal age? A study of teenagers in Estonia during the period of major socio-economic changes (from 1992 to 2002)

OBJECTIVE: To assess the risk of low birth weight, preterm birth, stillbirth, neonatal and postneonatal death among primiparous teenagers having singleton births, compared to a similar group of women aged 20-24 years in Estonia during the period of major socio-economic changes. STUDY DESIGN: Registry study using the data from the Estonian Medical Birth Registry (EMBR) for years 1992-2002; EMBR data were linked with infant deaths in the Estonian Mortality Database. Study population included 51,890 women aged 13-24 years, arranged into three groups: < or =17, 18-19, and 20-24. Crude odds ratios (OR), adjusted ORs and their 95% confidence intervals (CI) for the different outcomes were estimated using multiple logistic regression analysis. RESULTS: Compared with women aged 20-24 years, the risk of low birth weight and preterm birth was higher among teenagers. The risk of low birth weight and preterm birth within the study group as a whole did not change during the study period. Increased risks in neonatal and postneonatal death among younger teenagers of an age of 17 years and less seem to be a result of prematurity. CONCLUSIONS: Despite major socio-economic changes resulting in improvements in obstetric care and growth in incomes, teenagers remained a higher risk group.     

Count every newborn: EN-BIRTH study improving facility-based coverage and quality measurement in routine information systems

Background

An estimated >2 million babies stillborn around the world each year lack visibility. Low- and middle-income countries carry 84% of the burden yet have the least data. Most births are now in facilities, hence routine register-recording presents an opportunity to improve counting of stillbirths, but research is limited, particularly regarding accuracy. This paper evaluates register-recorded measurement of hospital stillbirths, classification accuracy, and barriers and enablers to routine recording.

Methods

The EN-BIRTH mixed-methods, observational study took place in five hospitals in Bangladesh, Nepal and Tanzania (2017–2018). Clinical observers collected time-stamped data on perinatal care and birth outcomes as gold standard. To assess accuracy of routine register-recorded stillbirth rates, we compared birth outcomes recorded in labour ward registers to observation data. We calculated absolute rate differences and individual-level validation metrics (sensitivity, specificity, percent agreement). We assessed misclassification of stillbirths with neonatal deaths. To examine stillbirth appearance (fresh/macerated) as a proxy for timing of death, we compared appearance to observed timing of intrauterine death based on heart rate at admission.

Results

23,072 births were observed including 550 stillbirths. Register-recorded completeness of birth outcomes was > 90%. The observed study stillbirth rate ranged from 3.8 (95%CI = 2.0,7.0) to 50.3 (95%CI = 43.6,58.0)/1000 total births and was under-estimated in routine registers by 1.1 to 7.3 /1000 total births (register: observed ratio 0.9–0.7). Specificity of register-recorded birth outcomes was > 99% and sensitivity varied between hospitals, ranging from 77.7–86.1%. Percent agreement between observer-assessed birth outcome and register-recorded birth outcome was very high across all hospitals and all modes of birth (> 98%). Fresh or macerated stillbirth appearance was a poor proxy for timing of stillbirth. While there were similar numbers of stillbirths misclassified as neonatal deaths (17/430) and neonatal deaths misclassified as stillbirths (21/36), neonatal deaths were proportionately more likely to be misclassified as stillbirths (58.3% vs 4.0%). Enablers to more accurate register-recording of birth outcome included supervision and data use.

Conclusions

Our results show these routine registers accurately recorded stillbirths. Fresh/macerated appearance was a poor proxy for intrapartum stillbirths, hence more focus on measuring fetal heart rate is crucial to classification and importantly reduction in these preventable deaths.

     

Stillbirth and infant mortality among Hispanic singletons, twins, and triplets in the United States

OBJECTIVE: We estimate the impact of increasing fetal number on fetal and infant mortality among Hispanic mothers. METHODS: Retrospective cohort study involving singletons, twins, and triplets delivered in the United States from 1995 through 2000, except for the analysis on infant mortality in singletons (1995 through 1999). Main outcome measures were stillbirth (> or = 20 weeks) and infant mortality (< 365 days). RESULTS: A total of 37,489,600 individual births were reviewed, consisting of 36,840,704 singletons, 613,930 twins, and 34,966 triplets. Hispanics accounted for 6,848,027 (18.6%) singletons, 85,887 (14.0%) individual twins, and 2,725 (7.8%) individual triplets. Among singletons, stillbirth (odds ratio [OR] 0.91, 95% confidence interval [CI] 0.90-0.92) and infant mortality (OR 0.85, 95% CI 0.84-0.86) were both lower in Hispanics than in whites. Among twins, Hispanics had a lower risk for infant mortality (OR 0.93, 95% CI 0.88-0.97) but a comparable risk for stillbirth (OR 1.06, 95% CI 0.98-1.13). Although the risk for infant mortality in Hispanic triplets was comparable to that of whites (OR 1.20, 95% CI 0.94-1.54), Hispanic triplets had a 50% higher likelihood of dying in utero (OR 1.50, 95% CI 1.06-2.14). CONCLUSION: Although Hispanic infants generally show better or comparable survival indices compared with whites, the risk for fetal and infant death in Hispanics increases in fetal number in a dose-dependent fashion, thereby obliterating the Hispanic advantage. The elevated risk for stillbirth among Hispanic triplets is particularly noteworthy and underscores the need for caution in making generalizations of favorable birth outcomes in Hispanics.     

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.     

Mode of delivery and risk of stillbirth and infant mortality in triplet gestations: United States, 1995 through 1998

OBJECTIVE: The purpose of this study was to estimate the risks of stillbirth and neonatal and infant deaths in triplets, according to mode of delivery. STUDY DESIGN: We used the "matched multiple birth" data file that was comprised of triple births that were delivered in the United States in the years 1995 through 1998. Analyses were restricted to fetuses that were delivered at >/=24 weeks of gestation. Based on the order of the birth of the fetuses within the triplet set, the mode of delivery of triplets was assigned as cesarean-cesarean-cesarean (all cesarean), vaginal-vaginal-vaginal (all vaginal), and vaginal-cesarean-cesarean or vaginal-vaginal-cesarean (other). Associations between mode of delivery and stillbirth, neonatal deaths (within 28 days), and infant deaths (up to 1 year) were expressed as relative risks with 95% confidence intervals and population attributable risks, which were derived from multivariate logistic regression models that were based on the method of generalized estimated equations (with all cesarean deliveries serving as the reference). All analyses were adjusted for several confounding factors. RESULTS: Ninety-five percent of all triplets were delivered by cesarean delivery. Vaginal delivery (all vaginal) was associated with an increased risk for stillbirth (relative risk, 5.70; 95% CI, 3.83, 8.49) and neonatal (relative risk, 2.83; 95% CI, 1.91, 4.19) and infant (relative risk, 2.29; 95% CI, 1.61, 3.25) deaths. The population-attributable risks were 15.9% for neonatal and 12.4% for infant deaths, which implied that these proportions of deaths were potentially avoidable had these triplet fetuses all been delivered by cesarean delivery rather than all fetuses being delivered vaginally. CONCLUSION: Cesarean delivery of all 3 triplet fetuses is associated with the lowest neonatal and infant mortality rate. Vaginal delivery among triplet gestations should be avoided.     

A case-control study of unexplained antepartum stillbirths.

OBJECTIVE: To ascertain factors that will identify women who are at increased risk of unexplained antepartum stillbirth. DESIGN: Matched case-control study. The cases and controls were initially analysed as a whole group and again after dichotomizing into those of low birthweight (< 2500 g) and those of normal birthweight (> or = 2500 g). SETTING: Western Australia 1980-1983. SUBJECTS: Unexplained antepartum stillbirths of > or = 1000 g birthweight (cases) and liveborn infants individually matched for year of birth, plurality, sex and birthweight of infant and race of mother (controls). RESULTS: The case pregnancies had more polyhydramnios (OR 10.83, 95% CI 2.41-48.69) and cord problems (OR 6.57 95% CI 1.36-31.75) than the controls but, paradoxically, other obstetric and medical complications were less common in the cases. The association with polyhydramnios persisted when the analysis was confined to those with low birthweight. With normal birthweight fetal distress was more frequent in the cases (OR 3.65 95% CI 1.36-9.80) but there were few other differences. CONCLUSIONS: The clinical and diagnostic systems currently in use are unable to identify many fetuses at risk of death. Decreases in the rate of unexplained antepartum stillbirths await the discovery of new preventable causes, or of innovations in clinical or laboratory aspects of obstetric care.     

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.     

Mode of delivery and the risk of delivery-related perinatal death among twins at term: a retrospective cohort study of 8073 births

OBJECTIVE: To determine the risk of perinatal death among twins born at term in relation to mode of delivery. DESIGN: Retrospective cohort study. SETTING: Scotland 1985-2001. POPULATION: All twin births at or after 36 weeks of gestation, excluding antepartum stillbirths and perinatal deaths due to congenital abnormality (n= 8073). METHODS: The outcome of first and second twins was compared using McNemar's test and the outcome of twin pairs in relation to mode of delivery was compared using exact logistic regression. MAIN OUTCOME MEASURES: Intrapartum stillbirth or neonatal death of either twin. RESULTS: Overall, there were six deaths of first twins and 30 deaths of second twins (OR for second twin 5.00, 95% CI 2.00-14.70). The odds ratio for death of the second twin due to intrapartum anoxia was 21 (95% CI 3.4-868.5). The associations were similar for twins delivered following induction of labour and for sex discordant twins. However, there was no association between birth order and the risk of death among 1472 deliveries by planned caesarean section. There was death of either twin among 2 of 1472 (0.14%) deliveries by planned caesarean section and 34 of 6601 (0.52%) deliveries by other means (P= 0.05, odds ratio for planned caesarean section 0.26 [95% CI 0.03-1.03]). The association was similar when adjusted for potential confounders. Assuming causality, we estimate that 264 caesarean deliveries (95% CI 158-808) would be required to prevent each death. CONCLUSION: Planned caesarean section may reduce the risk of perinatal death of twins at term by approximately 75% compared with attempting vaginal birth. This is principally due to reducing the risk of death of the second twin due to intrapartum anoxia.     

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.     

Birth weight discordancy and adverse perinatal outcomes among twin gestations in the United States: the effect of placental abruption

OBJECTIVE: We evaluated whether the relationship between birth weight discordancy of twins and stillbirth, neonatal deaths, and preterm births was modified by the presence of abruption. STUDY DESIGN: We used the 1995 to 1997 matched multiple birth file for United States twin births (n = 269287). Birth weight discordancy was defined as the ratio of the difference in birth weight of the heavier from the lighter twin to that of the heavier twin and was categorized as <5%, 5% to 9%, 10% to 14%, 15% to 19%, 20% to 29%, 30% to 39%, and >or=40%. We evaluated the risks of stillbirth (>or=20 weeks of gestation), neonatal deaths (within 28 days after birth), and preterm birth (< 32 weeks) in the presence and absence of abruption. Associations between birth weight discordancy and these perinatal outcomes were expressed as adjusted relative risks and were derived from multivariable logistic regression models, based on the method of generalized estimating equations. Risk of these outcomes were derived for each stratum of birth weight discordancy and abruption status, with the <5% birth weight discordancy, nonabruption status labeled as the reference group. All analyses were performed separately for same and different sex twins. RESULTS: A birth weight discordancy of >or=20% among same sex (adjusted relative risk, 1.2; 95% CI, 1.1, 1.4), and >or=40% among different sex twins (relative risk, 2.2; 95% CI, 1.7, 2.8) conferred increased risk for abruption. Among nonabruption births, a birth weight discordancy of >or=15% among same sex and >or=30% among different sex twins increased the risk of stillbirths, neonatal deaths, and preterm births. Among abruption births, however, the risks were increased even in the lowest birth weight discordancy category (<5%). The relative risks of stillbirths and neonatal deaths among abruption births were significantly higher for each birth weight discordancy group, both for same and different sex twins, compared with the reference group. The association between birth weight discordancy and preterm birth was not modified by either the presence or absence of abruption. CONCLUSION: Birth weight discordancy of >or=15% for same sex and >or=30% for different sex confer greatest risk of adverse perinatal outcomes in the absence of abruption. In the presence of placental abruption, these risks are further compounded. The results underscore the need for careful monitoring of twin pregnancies.