Faculty Bibliography

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/CONCLUSIONS: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.

OBJECTIVE: To construct an institution-specific nomogram of fetal abdominal circumference measurements and determine whether previously published nomograms correctly categorize our population's outer centiles. DESIGN: Using cross-sectional data from a database of sonographic circumference measurements, a nomogram for abdominal circumference measurements was created by modeling the mean and standard deviation separately. The adequacy of the nomogram was confirmed by assessing the normal distribution of data, verifying goodness-of-fit, and checking residuals. Outer centiles were compared with those from other published nomograms. RESULTS: The new nomogram for fetal abdominal circumference measurements from 10 070 fetuses provided sufficient data to derive values for the 5th, 10th, 50th, 90th and 95th centiles based on gestational age. Comparisons with other published nomograms indicated that the false-negative rates for classifying our population as < 10th centile or > 90th centile ranged from 11.3% to 90.5% and from 0 to 66.4%, respectively. CONCLUSION: Institution-specific nomograms of fetal abdominal circumference measurements are important to avoid incorrect categorization of outer centiles

OBJECTIVES: To assess the role of cervical sonography and to compare various sonographic cervical parameters in their ability to predict spontaneous preterm birth in high-risk singleton gestations. DESIGN: A prospective cohort of 469 high-risk gestations were longitudinally evaluated between 15 and 24 weeks' gestation on 1265 occasions with transvaginal cervical sonography and transfundal pressure. The cervical parameters obtained were funnel width and length, cervical length, percent funneling and cervical index. The information obtained was used for patient management. Restriction of physical activities was initiated at cervical lengths of < or = 2.5 cm with cerclage as an option for cervical lengths of < or = 2.0 cm. RESULTS: Receiver operating characteristic curve analyses showed that a cervical length of < or = 2.5 cm between 15 and 24 weeks' gestation was equal to the other sonographic cervical parameters in its ability to predict spontaneous preterm birth. The sensitivities for delivery at < 28, < 30, < 32 and < 34 weeks' gestation were 94%, 91%, 83% and 76%, respectively, while the negative predictive values were 99%, 99%, 98% and 96%, respectively. The placement of a cerclage did not influence the positive and negative predictive values. In comparison to women with other risk factors, cervical length was best in the prediction of preterm birth in women with a prior mid-trimester loss; an optimal cut-off of < or = 1.5 cm had sensitivities for delivery at < 28, < 30, < 32 and < 34 weeks' gestation of 100%, 100% 92% and 81%, respectively. The rate of preterm delivery at < 34 weeks' gestation increased dramatically when the cervical length was < or = 1.5 cm. Cervical length was the only independent variable that entered the logistic regression model for the prediction of preterm delivery at < 34 weeks' gestation. CONCLUSIONS: In high-risk singleton gestations a cervical length of < or = 2.5 cm was equal to other sonographic cervical parameters in its ability to predict spontaneous preterm birth and was better for the prediction of earlier forms of prematurity (at < 28 and < 30 weeks) than later forms (at < 32 and < 34 weeks). The optimal cervical lengths and their performance for predicting prematurity may be influenced by obstetric risk factors

The objective of this study was to determine the frequency of prenatally diagnosed unilateral cerebral ventriculomegaly and also to assess neonatal outcome in infants with this prenatal diagnosis. A computerized ultrasonography database identified fetuses with isolated and nonisolated unilateral cerebral ventriculomegaly from October 1994 to June 1999. The Denver II Developmental Screening Test was used to assess developmental skills. Unilateral cerebral ventriculomegaly was diagnosed in 15 of 21,172 (1 per 1,411) pregnancies. The width of the enlarged lateral ventricle ranged from 1.0 to 1.9 cm. In 10 (67%) of 15 cases unilateral cerebral ventriculomegaly was an isolated finding. Eight of the 14 infants who were born at 36 weeks' gestation or later had postnatal cranial imaging, and ventricular asymmetry was confirmed in 5 (63%). One infant with an arachnoid cyst and cerebral palsy died at 2 years of age. The remaining 11 infants in whom developmental milestones were assessed had age-appropriate skills. Unilateral fetal ventriculomegaly is usually an isolated finding and when isolated has little measurable effect on developmental outcome

One of the most important advances in perinatal health care is the use of antepartum fetal testing. Antepartum fetal testing methods may include inexpensive tests such as fetal kick counts or tests that can be quite expensive such as non-stress tests, fetal biophysical profiles, and Doppler assessments as well as invasive tests such as amniocentesis or cordocentesis. Clinical experience, combined with recent literature, suggest that there is no ideal test for all high-risk fetuses and that some antepartum fetal tests may be more appropriate than others, depending on the underlying pathophysiology or the indication for testing. Because many different pathophysiological processes lead to fetal acidemia and in-utero death, indication-specific testing may be not only logical, but also cost-effective. In this article, specific guidelines of antepartum fetal testing are presented. These indication-specific guidelines are based on the underlying pathophysiological processes that place the fetus at risk and also on the need to use the fewest number of tests without compromising safety.

OBJECTIVE:The objective of this study was to perform a cost-benefit analysis of routine second-trimester screening ultrasonography in the United States as compared with performing ultrasonography only in the presence of indications. STUDY DESIGN/METHODS:It was assumed that 1 million pregnant women are available annually who otherwise would not have an indication for an ultrasonographic examination. Cost savings from early detection and therapeutic abortion were considered only for fetal conditions for which lifetime cost estimates are available, including spina bifida, major cardiac disease, cleft lip or palate, renal agenesis or dysgenesis, urinary obstruction, lower or upper limb reduction, omphalocele, gastroschisis, and diaphragmatic hernia. Two separate cost-benefit analyses were considered with the range of fetal anomaly detection rates before 24 weeks' gestation as reported by tertiary and non-tertiary centers in the Routine Antenatal Diagnostic Imaging with Ultrasound (RADIUS) trial. Potential cost savings from averting treatment for preterm labor and postdate gestations were also considered. RESULTS:The ratio of savings to cost was between 1.35 and 1.70 (savings of $1.35-$1.70 per $1 spent) if the ultrasonographic examinations were performed in tertiary care centers. The ratio of savings to cost was between 0.40 and 0.74 (loss of $0.26-$0.60 per $1 spent) if the examinations were performed in nontertiary centers. If the screening ultrasonography was performed in tertiary centers, the expected annual net benefits were estimated at $97 to 189 million. If ultrasonographic screening was performed in nontertiary centers, the expected annual net losses were estimated at $69 to 161 million. CONCLUSION/CONCLUSIONS:Routine second-trimester ultrasonographic screening appears to be associated with net benefits only if the ultrasonography is performed in tertiary care centers.

OBJECTIVE:To compare the cost and benefits of prenatal diagnosis for Down syndrome using the British and American approaches. METHODS:This cost-benefit analysis was based on a decision-analytic approach. The British strategy included screening by a first-trimester ultrasound at 10-14 weeks for nuchal translucency thickness, and the American strategy included only second-trimester screening by using maternal age and maternal serum screening. The key probabilities of the decision-tree analysis and all cost estimates were based on American standards. The best scenario of the British strategy assumed ultrasound nuchal translucency thickness sensitivity (for detecting Down syndrome) of 80% and a false-positive rate of 5% and the worst scenario assumed a sensitivity of 50% and a false-positive rate of 10%. The results were expressed in annual costs based on approximately 4 million births per year in the United States. RESULTS:As compared with do-nothing, the American strategy was found to allow savings of approximately $96 million per year and the best scenario for the British strategy was savings of approximately $5 million per year. The financial costs of the British and American strategies would be comparable only if the first-trimester ultrasound had a sensitivity of 80% and a false-positive rate of 5% in detecting Down syndrome. CONCLUSION/CONCLUSIONS:The British strategy does not appear to be economically beneficial in the United States even under the most ideal scenarios of ultrasound accuracy.

OBJECTIVE:To estimate the 16-week prevalence of Down syndrome in the United States from 1974 to 1997 and to determine the efficacy of maternal age cutoffs and triple screens for detecting it antenatally. METHODS:Using natality statistics for the United States from 1974 to 1997 of maternal-age-specific live births to women 13-49 years old, we evaluated advanced maternal age (35-49 years at delivery) and the triple serum test (maternal serum alpha-fetoprotein, hCG, and unconjugated estriol) as screening tests for Down syndrome. Efficacy was evaluated using sensitivity, false-positive rate, positive predictive value, and likelihood ratio (likelihood ratio = sensitivity/false-positive rate). RESULTS:In 1974, the estimated second-trimester prevalence of Down syndrome was one in 740, but by 1997 that had increased to one in 504. The proportion of Down syndrome fetuses at 16 weeks' gestation in women 35-49 years old increased from 28.5% in 1974 to 47.3% in 1997. However, live births to women 35-49 years old increased more rapidly from 4.7% in 1974 to 12.6% in 1997. The likelihood ratio for maternal age to identify an affected pregnancy decreased during the study period and was substantially lower than that using the serum test. CONCLUSION/CONCLUSIONS:A maternal age cutoff of 35 years in the 1990s resulted in high false-positive rates and was less efficacious based on likelihood ratio and positive predictive value. Serum testing of all pregnant women would reduce the number of amniocenteses and decrease procedure-related losses.

OBJECTIVE:To determine the incidence and trends of twinning in the United States and to review the medical and economic effects of twin versus singleton gestations. METHODS:Pertinent and recent studies on twin gestations were obtained through a MEDLINE database search of the English language between December 1987 and December 1999. Data from the 1995-1996 National Center for Health Statistics were also used to compare gestational age at delivery, fetal growth restriction, and perinatal mortality for twin and singleton gestations. Studies that have evaluated perinatal risks in relation to advanced reproductive technology also were reviewed and summarized. The economic implications of twinning from a societal perspective and infant quality of life issues of twins compared with singleton gestations are reviewed. RESULTS:Due to delayed childbearing and increased use of reproductive technologies, the incidence of twin gestations in the United States has been increasing. Twin pregnancies have a higher risk of complications, including pregnancy-induced hypertension, anemia, antepartum and postpartum hemorrhage, and maternal mortality. In addition, twin infants are more likely to deliver preterm, have low birth weight and greater perinatal mortality rates. These outcomes influence health care costs and quality of life for both parents and children. CONCLUSIONS:Women carrying twin fetuses are at increased risk for perinatal and obstetric complications. The increased perinatal risks that accompany twin fetuses may be partly due to the increasing use of advanced reproductive technologies. The economic burdens, as well as the potential for decreased quality of life among twins, needs careful evaluation.