Faculty Bibliography

OBJECTIVE:The purpose of this study was to compare risk factor profiles for placenta previa between singleton and twin live births. STUDY DESIGN/METHODS:This cohort study was based on United States natality data files (1989 through 1998) and comprised 37,956,020 singleton births and 961,578 twin births. Women who were diagnosed with placenta previa were included only if they were delivered by cesarean delivery. Risk factors for placenta previa that were examined included sociodemographic (age, gravidity, education, marital status, and race), behavioral (prenatal care, smoking, and alcohol use), previous preterm birth, and medical and obstetric factors. Effect modification between maternal age and gravidity and the dose-response relationship with number of cigarettes smoked/day on placenta previa risk were also evaluated. RESULTS:The rate of placenta previa was 40% higher among twin births (3.9 per 1,000 live births, n = 3,793 births) than among singleton births (2.8 per 1,000 live births, n = 104,754 births). Comparison of risk factors for placenta previa between the singleton and twin births revealed fairly similar risk factor profiles. Compared with primigravid women <20 years old, the risk for placenta previa increased by advancing age and by increasing number of pregnancies among both singleton and twin births. The number of cigarettes smoked per day also showed a dose-response trend for placenta previa risk in the two groups. CONCLUSION/CONCLUSIONS:The increased rate of placenta previa among twin births underscores the need to monitor carefully such pregnancies with heightened suspicion and awareness for the development of this condition.

OBJECTIVE:This study was undertaken to determine whether intrapartum fevers at term are associated with markers of acute inflammation in maternal, fetal, and placental compartments. STUDY DESIGN/METHODS:Term cases with intrapartum fever (temperature >/=100.4 degrees F) were recruited with gestational age-matched controls. Maternal serum and umbilical vein blood were collected and assayed for interleukin-6 (IL-6) levels. Placentas were examined for histologic chorioamnionitis. Demographic and clinical data were collected and compared between cases and controls. RESULTS:Forty-seven case-control pairs were analyzed. Maternal IL-6 levels were higher in cases than in controls (median of 145 pg/mL vs 42 pg/mL, P <.0001). Umbilical vein IL-6 levels also were higher in cases than controls (median 9 pg/mL vs 3.5 pg/mL, P =.01), but more than half of levels in cases were below 11 pg/mL. Only 31.1% of febrile cases had moderate or severe histologic chorioamnionitis. Multivariable logistic regression identified maternal serum IL-6 levels, nulliparity, and number of vaginal examinations as the major predictors of intrapartum fever at term. CONCLUSION/CONCLUSIONS:The maternal inflammatory response as measured by maternal serum IL-6 levels is a strong marker for term intrapartum fever. The much weaker association of fetal and placental inflammatory responses suggest a smaller than expected contribution of intra-amniotic inflammation to term intrapartum fevers.

OBJECTIVE: This study was undertaken to construct an institution-specific transverse cerebellar (transcerebellar) diameter nomogram with special emphasis in the third trimester and to compare its ability to predict gestational age with previously published nomograms. STUDY DESIGN: A cross-sectional nomogram was constructed using transcerebellar diameter measurements in 24,026 well-dated singleton fetuses by using linear regression models. Third-trimester measurements from 2,010 fetuses were included. The performance of previously established transcerebellar diameter nomograms for predicting gestational age was assessed in our population to determine comparability between nomograms. RESULTS: Interobserver and intraobserver variabilities in the second and third trimesters were 3.1% to 3.7% and 3.4% to 3.8%, respectively. Between 14 and 27 weeks' gestation, there were no clinically important differences between our nomogram and those previously published in terms of the predicted gestational age. However, predicted gestational age in the third trimester was considerably different by using our nomogram by 1 to 2 weeks from 28 to 30 weeks and by 4 to 6 weeks after 32 weeks. CONCLUSION: Transcerebellar measurements had a similar relationship with gestational age across previously published nomograms before 28 weeks. However, clinically significant differences in predicting gestational age appear later, especially after 32 weeks. These findings suggest that this new nomogram may be particularly useful for accurate dating of pregnancies in the third trimester.

OBJECTIVE: To describe the prenatal detection of fetal trisomy 18 through abnormal sonographic features and to determine the sensitivity of sonographically detecting fetuses with trisomy 18. METHODS: All genetic and cytogenetic records of fetuses with trisomy 18 were reviewed retrospectively (1992-2002). From these, singleton fetuses who had prenatal sonography at our unit were identified. The maximal numbers of individual abnormalities from 1 sonographic examination (not limited to type of organ system) were recorded. Each abnormality was classified as major, minor, or 'other,' and each organ system was classified as abnormal only once, regardless of the number of individual abnormalities identified in that system. The sensitivity of sonography in detecting abnormalities of trisomy 18 was determined. RESULTS: Of 38 fetuses identified with trisomy 18, all had 4 or more prenatally detected sonographic abnormalities (sensitivity of sonographic detection of fetuses with trisomy 18, 100%). The median number of abnormalities per examination was 8 (range, 4-19). Sonographically detected major abnormalities were cardiac (84%; n = 32), central nervous system (87%; n = 33), gastrointestinal (26%; n = 10), and genitourinary (16%; n = 6). Sonographically detected minor abnormalities were short ear length below the 10th percentile for gestational age (96%; n = 26/27), upper extremities and hands (95%; n = 36), lower extremities and feet (63%; n = 24), and face (53%; n = 20). Fifty percent (19 of 38) had choroid plexus cysts identified, but this was never an isolated finding. CONCLUSIONS: In experienced hands, the sensitivity of detecting fetal trisomy 18 on prenatal sonography is 100%, and all cases will have multiple anomalies visualized

OBJECTIVE: To determine the usefulness of a fetal ear length nomogram in the prenatal detection of fetal aneuploidy and to determine whether ear smallness in cases of aneuploidy is a primary or secondary event. METHODS: Ear lengths of 447 singleton fetuses (October 1996 to October 1997)were prospectively evaluated between 14 and 41 weeks to establish a nomogram created by modeling the mean and SD separately. Records of aneuploid fetuses were retrospectively reviewed, and their ear lengths were plotted against the nomogram to determine detection rates, with ear length in or below the 10th and 50th percentiles for a given gestational age and biparietal diameter used as abnormal cutoffs. RESULTS: The nomogram for fetal ear length measurements provided sufficient data to derive the 10th, 50th, and 90th percentiles on the basis of gestational age and biparietal diameter. The ear length of euploid fetuses was significantly correlated with gestational age (R2 = 0.96; P < .001) and biparietal diameter (R2 = 0.95; P < .001). From 96 aneuploid fetuses identified, 63 had ear lengths in or below the 10th percentile for gestational age (sensitivity, 66%). When using ear length against biparietal diameter, the sensitivities for all aneuploid fetuses for cutoffs at or below the 10th and 50th percentiles were 43% (40 of 93) and 83% (77 of 93), respectively. CONCLUSIONS: Most aneuploid fetuses have sonographically small ears (< or = 10th percentile for gestational age). This smallness is not entirely related to overall small fetal size, but in almost half the cases, the fetal ear length is disproportionately smaller than the biparietal diameter

As genetic research and technology continues to expand, carrier testing for an increasing number of single gene disorders is becoming available. Tay-Sachs disease and cystic fibrosis are two common recessive conditions with large-scale health implications. Tay-Sachs disease was the first genetic disorder for which community-based screening efforts were utilized and has provided a foundation for the development of other screening programs. Cystic fibrosis testing, on the other hand, has additional complexities and the implementation of population-based screening has been under debate. The many issues (technical, educational, social, psychological and economical) which must be considered as preconceptional and prenatal genetic screening is incorporated into clinical practice are discussed here in the context of Tay-Sachs disease and cystic fibrosis.

OBJECTIVE:The purpose of this study was to determine the incidence of trisomy 18 in women who are <35 years old and who have sonographically detected isolated choroid plexus cyst. STUDY DESIGN/METHODS:A meta-analysis of prospective trials that were published in the English language between 1990 and 2000 was performed. Each trial met the following inclusion criteria: (1) prospective trial, (2) total population screened during the study period reported, (3) maternal age (either numeric or descriptive) reported, and (4) pregnancy/neonatal outcomes reported. An isolated choroid plexus cyst for the purpose of this study was defined as absence of sonographically detected structural abnormalities and normal serum analyte screens, if reported. RESULTS:Eight trials met the criteria and were used for analysis. A total of 106,732 women were screened through articles that were published between 1990 and 2000. The total number of fetuses with choroid plexus cysts that were identified in second-trimester scans were 1,235 (incidence, 1.2%). The incidence of isolated choroid plexus cysts in women who were <35 years old was 1.0% (n = 1,017 women). There were no cases of trisomy 18 in women with isolated choroid plexus cyst who were <35 years old. Four structural abnormalities were noted on postnatal examination; all four neonates had normal karyotypes. CONCLUSION/CONCLUSIONS:There is no evidence that detection of isolated choroid plexus cyst in women who are <35 years of age increases the risk of trisomy 18. Therefore, amniocentesis is not warranted because of the inherent risk of pregnancy loss that is associated with the procedure. Better algorithms are needed to screen women who have a low risk for trisomy 18.

OBJECTIVE:Our purpose was to evaluate the association between birth weight (BW) and fetal death (FD) among pregnant nondiabetic and diabetic patients. STUDY DESIGN/METHODS: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/CONCLUSIONS:The FD rate is increased when birth weight is > or =4250 g in nondiabetic patients and > or =4000 g in diabetic patients.