Faculty Bibliography

OBJECTIVE: This study was undertaken to determine the accuracy of our previously published and prospectively validated institution-specific singleton transcerebellar diameter (TCD) nomogram in the prediction of gestational age (GA) in twin pregnancies. We further evaluated whether the prediction of GA in twin gestations using the singleton TCD nomogram differs between monochorionic and dichorionic twins. STUDY DESIGN: In our previously published studies, we retrospectively constructed a cross-sectional nomogram using TCD measurements in 24,026 well-dated, singleton fetuses, and prospectively validated the nomogram using 2,597 singleton fetuses. The current study comprised of 1,278 well-dated twins (19.6% monochorionic) seen in our ultrasound unit between August 1994 and May 2003, and the singleton TCD nomogram was validated in these twin gestations. The actual GA was subtracted from the GA predicted by the TCD nomogram and the concordance between actual and predicted GAs was assessed on the basis of the Pearson's correlation coefficient (r). This was performed separately for monochorionic and dichorionic twins. RESULTS: Concordance between the actual and predicted twin TCD measurements based on our previously published singleton TCD nomogram was high (Pearson's correlation, r = 0.95, P < .0001). Between 16 and 23 weeks' gestation, the predicted mean GA was within 6 days of actual GA. Between 24 and 30 weeks, the predicted mean GA was within 3 days, and at 32 weeks or more, the predicted mean GA was within 5 days of the actual GA. Prediction of GA based on the singleton TCD nomogram was equally accurate in both monochorionic and dichorionic twin gestations (P = .686). CONCLUSION: This study demonstrates that our previously validated singleton TCD nomogram is reliable and accurate in twins irrespective of placental chorionicity.

OBJECTIVE:Despite the recent increase in preterm birth in the United States, trends in preterm birth subtypes have not been adequately examined. We examined trends in preterm birth among singletons following ruptured membranes, medical indications, and spontaneous preterm birth and evaluated the impact of these trends on perinatal mortality. METHODS:A population-based, retrospective cohort study comprising 46,375,578 women (16% blacks) who delivered singleton births in the United States, 1989 through 2000, was performed. Rates of preterm birth (< 37 weeks), their subtypes, and associated perinatal mortality (stillbirths at >/= 22 weeks plus neonatal deaths within 28 days), before and after adjustment for potential confounders, were derived from ecological logistic regression models. RESULTS:Preterm birth rates increased by 14% (95% confidence interval 13-15%) among whites from 8.3% to 9.4% and decreased by 15% (95% confidence interval 14-16%) among blacks from 18.5% to 16.2% between 1989 and 2000. Among whites, preterm birth following ruptured membranes declined by 23%, medically indicated preterm birth increased by 55%, and spontaneous preterm birth increased by 3%. Among blacks, preterm birth following ruptured membranes declined by 37%, medically indicated preterm birth increased by 32%, and spontaneous preterm birth decreased by 27%. The largest decline in perinatal mortality among whites was associated with increases in medically indicated preterm birth, whereas the largest decline in perinatal mortality among blacks was associated with declines in preterm birth following ruptured membranes and spontaneous preterm birth. CONCLUSION/CONCLUSIONS:Temporal trends in preterm birth varied substantially based on underlying subtype and maternal race. The recent increase in medically indicated preterm birth was associated with a favorable reduction in perinatal mortality.

Anterior sacral meningocele is a rare condition resulting from herniation of the meninges through a sacral defect. Women with this condition may undergo inappropriate surgery because the correct diagnosis is missed, resulting in serious complications. In labor, the cyst may rupture, with consequent meningitis and high maternal mortality. We report the case of a 31 year-old pregnant woman with an anterior sacral meningocele. We describe the role of magnetic resonance imaging in the evaluation and management planning in this condition. She was delivered by cesarean section at 34 weeks without complications. Accurate diagnosis and delivery by cesarean prior to labor are important in assuring good outcomes in women with anterior sacral meningoceles.

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/METHODS: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/CONCLUSIONS: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.

OBJECTIVE:The purpose of this study was to examine if neonatal mortality rates (NMR) based on birth weight discordance (BWD) differ based on mode of delivery. STUDY DESIGN/METHODS:The population-based US "matched multiple birth" database (1995 to 1998) was used to examine the effect of vaginal/vaginal (VV) and cesarean/cesarean (CC) modes of delivery (MOD) on neonatal mortality (<28 days after birth). Births at <32 weeks, congenital malformations, chromosomal anomalies, and discordant MOD (vaginal/cesarean) were excluded. The association between MOD (with CC as the reference) and neonatal mortality was expressed as relative risks (RR) with 95% CI, derived from logistic regression models. RESULTS:The NMR increased with increasing degrees of BWD regardless of mode of delivery. CC was associated with decreased NMR when BWD was between 20% and 40%, but this reached significance at BWD > or =40%; VV pairs had a 1.6-fold (95% CI 1.1-2.2) increased NMR compared with CC. CONCLUSION/CONCLUSIONS:In twins with BWD <40%, MOD has no effect on NMR. Beyond or equal to 40% discordance, there was lower NMR with cesarean-cesarean delivery.

OBJECTIVE:The purpose of this study was to evaluate temporal trends in abruption risk and to assess how much underlying changes in the clinical determinants may have affected these trends. STUDY DESIGN/METHODS:We used the National Hospital Discharge Summary data (1979-2001), an annual survey of sampled non-federal, short stay, general, and specialty hospitals in the United States. Trends in abruption were assessed for the periods 1979 through 1981 and 1999 through 2001. Clinical determinants of abruption that were evaluated included hypertensive diseases, anemia, gestational diabetes mellitus, preterm labor, preterm premature rupture of membranes, chorioamnionitis, oligohydramnios, obstetric shock/trauma, uterine tumors, short umbilical cord, and velamentous cord insertion. Temporal trends in abruption were examined before and after adjustment for determinants through multivariable logistic regression. RESULTS:The rate of abruption increased 92% (95% CI, 88, 96) among black women between 1979-1981 (0.76%; n = 13,584 women) and 1999-2001 (1.43%; n = 18,960 women). Among white women, the rate increased by 15% (95% CI, 14,16) over the same period, from 0.82% (n = 66,186 women) in 1979-1981 to 0.94% (n = 59,284 women) in 1999-2001. The determinants that were associated with trends in abruption included anemia, gestational diabetes mellitus, preterm labor, short umbilical cord, and velamentous cord insertion, although their effects varied substantially by maternal race. CONCLUSION/CONCLUSIONS:The temporal increase in rates of abruption may reflect a true increase in risk or may be the result of improved diagnosis of both abruption and its determinants. Although the cause of abruption is still speculative, the trend is of concern and deserves scrutiny.

OBJECTIVE:To estimate the incidence of delayed interval delivery in twin pregnancies in the United States and evaluate the impact of delayed delivery on perinatal outcomes. STUDY DESIGN/METHODS:A population-based retrospective cohort study was performed using the U.S. "matched multiple birth" file (1995 to 1998), restricting our analysis to twin sets in which the first twin was delivered vaginally at 22 to 28 weeks (n = 4257). Outcomes examined included perinatal and infant mortality and small-for-gestational-age births. Outcomes of second twins in pregnancies that underwent delayed interval delivery of 1, 2, 3, and >/=4 weeks were compared with those in which both twins were delivered contemporaneously. RESULTS:In this cohort, 6.1% (n = 258) of twins had delayed delivery (>/=1 week) of the second twin. Decreases in perinatal and infant mortality were observed only when the first twin was delivered at 22 to 23 weeks and when the delivery interval was </=3weeks. However, for intervals >/=4 weeks or when the first twin was delivered at 24 to 28 weeks (regardless of delivery interval), there was no benefit in perinatal or infant mortality. Delayed delivery of >/=4 weeks was associated with increased risk of small-for-gestational-age birth in the second twin, regardless of gestational age at delivery of the first. CONCLUSION/CONCLUSIONS:When a first twin was delivered at 22 to 23 weeks, delayed delivery of the second twin was associated with reduced perinatal and infant mortality of the second twin if the interval was less than 3 weeks. Delayed delivery of the second twin when the first was delivered at >/=24 weeks had no benefit on mortality.

OBJECTIVE:We examined trends in twin preterm birth <37 weeks following ruptured membranes (ROM), medically indicated preterm birth, and preterm birth following spontaneous onset of labor (PTL). We further examined whether the changes in preterm birth subtypes were associated with trends in twin perinatal mortality. STUDY DESIGN/METHODS:We carried out a retrospective cohort study of 1,172,405 twin live births and stillbirths delivered in the US between 1989 and 2000. Trends in preterm birth subtypes and perinatal mortality (stillbirths at > or = 22 weeks plus neonatal deaths within 28 days) were examined through ecological logistic regression models after adjusting for confounders. RESULTS:Twin preterm birth among whites increased from 46.6% in 1989 to 1990 to 56.7% in 1999 to 2000, and from 56.1% to 61.0% among blacks over the same period. Medically indicated preterm birth increased by 50% (95% CI 49-52) among whites, and by 33% (95% CI 29-36) among blacks. PTL increased by 24% among whites, but remained fairly unchanged among blacks between the two periods. Preterm birth following ROM also did not change between the 2 periods among whites, but declined by 7% among blacks. Perinatal mortality among twin births declined by 41% (95% CI 38-44) among whites, and by 37% (95% CI 32-42) among blacks between 1989 and 1990 and 1999 and 2000. This mortality decline was most closely associated with the increase in medically indicated preterm birth among whites, and with the decrease in preterm birth following ROM among blacks. CONCLUSION/CONCLUSIONS:Temporal trends in twin preterm birth varied substantially based on underlying subtypes and race. The increase in medically indicated preterm birth is associated with a large reduction in perinatal mortality.