Indications for caesarean sections at ≥34 weeks among nulliparous women and differential composite maternal and neonatal morbidity.

OBJECTIVE: To compare composite maternal and neonatal morbidities (CMM, CNM) among nulliparous women with primary indications for caesarean section (CS) as acute clinical emergency (group I; ACE), non-reassuring fetal heart rate (group II) and arrest disorder (group III). DESIGN: A multicentre prospective study. SETTING: Nineteen academic centres in the USA, with deliveries in 1999-2002. POPULATION: Nulliparous women (n = 9829) that had CS. METHODS: Nulliparous women undergoing CS for three categories of indications were compared using logistic regression model, adjusted for five variables. MAIN OUTCOME MEASURES: CMM was defined as the presence of any of the following: intrapartum or postpartum transfusion, uterine rupture, hysterectomy, cystotomy, ureteral or bowel injury or death; CNM was defined as the presence of any of the following: umbilical arterial pH <7.00, neonatal seizure, cardiac, hepatic, renal dysfunction, hypoxic ischaemic encephalopathy or neonatal death. RESULTS: The primary reasons for CS were ACE in 1% (group I, n = 114) non-reassuring FHR in 29% (group II; n = 2822) and failed induction/dystocia in the remaining 70% (group III; n = 6893). The overall risks of CMM and CNM were 2.5% (95% confidence intervals, CI, 2.2-2.8%) and 1.9% (95% CI 1.7-2.2), respectively. The risk of CMM was higher in group I than in group II (RR 4.1, 95% CI 3.1, 5.3), and group III (RR 3.2, 95% CI 2.7, 3.7). The risk of CNM was also higher in group I than in group II (RR 2.8, 95% CI 2.3, 3.4) and group III (RR 14.1, 95% CI 10.7, 18.7). CONCLUSIONS: Nulliparous women who have acute clinically emergent caesarean sections are at the highest risks of both composite maternal and neonatal morbidity and mortality.

The impact of route of delivery and presentation on twin neonatal and infant mortality: a population-based study in the USA, 1995-97.

OBJECTIVE: We examined whether the route of delivery for near-term (> or = 34 weeks' gestation) twins, as candidates for vaginal delivery, affected neonatal and infant mortality rates. We further evaluated whether these mortality rates were modified by fetal presentation. METHODS: A population-based retrospective cohort study based on the matched multiple births data in the USA (1995-97) was performed. Analyses were restricted to non-malformed liveborn twins delivered at (> or = 34 weeks' gestation. Twins with breech-breech and breech-vertex presentations were excluded, since they are not candidates for vaginal delivery. Neonatal mortality rates (death within the first 27 days) and post-neonatal mortality rates (death between 28 and 365 days) per 1000 twin live births, by route of delivery and fetal presentation, were derived. The associations between neonatal mortality, post-neonatal mortality and the route of delivery for vertex-breech versus vertex-vertex presentations were expressed based on relative risks (RR) and 95% confidence intervals (CI) derived from logistic regression models based on the method of generalized estimating equations. RESULTS: Of the 177,622 twins analyzed, 87% (n = 154,531) presented as vertex-vertex. Fifty-five per cent (n = 97,692) of twins were both delivered vaginally, 41% (n = 72,825) were both delivered by Cesarean section and, of the remaining 4% (n = 7,105), the first twin was delivered vaginally and the second by Cesarean section. Twins with vertex-breech presentations delivered by Cesarean-cesarean sections, as well as those with vertex-vertex presentations delivered vaginally, had the lowest neonatal mortality rate (1.6 per 1000 live births). The highest neonatal mortality rate in the vertex-breech pairs occurred with vaginal-Cesarean deliveries (2.7 per 1000 live births). Among twins with vertex-vertex presentations, twins delivered via the vaginal-Cesarean route experienced the highest neonatal mortality (3.8 per 1000 live births). The RR for neonatal mortality in this group was 2.24 (95% CI 1.35, 3.72) compared with twins both delivered vaginally. CONCLUSION: Route of delivery and fetal presentation both confer an impact on twin infant mortality rates. Strategies to reduce discordant routes in complicated vaginal deliveries may lead to improved neonatal survival.

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.

The effects of labor on infant mortality among small-for-gestational-age infants in the USA.

OBJECTIVE: To determine whether the presence of labor affects infant mortality among small-for-gestational-age (SGA) infants. METHODS: Data were derived from the United States national linked birth/infant death data sets for 1995-97. Singleton SGA live births in cephalic presentation delivered at 24-42 weeks' gestation were included. Mortality rates for SGA infants exposed and unexposed to labor were compared, and relative risks (RR) were derived using multivariable logistic regression models, after adjusting for potential confounding factors. RESULTS: Of 986 405 SGA infants, 87.4% were exposed to labor. Infants exposed to labor at 24-31 weeks had greater risks of dying during the early neonatal period (RR 1.79-1.86). Decreased risks of late and postneonatal death were observed at all gestational ages in the presence of labor. CONCLUSIONS: Exposure to labor is associated with an increased risk of early neonatal death among SGA infants, especially at gestational ages below 32 weeks. Future randomized trials are warranted to determine the optimal obstetric management of these high-risk infants.

Assessing genetic risk: comparison between the referring obstetrician and genetic counselor.

OBJECTIVE: To compare the genetic risk assessment of the referring obstetrician to the risk assessment of the genetic counselor. STUDY DESIGN: All patients evaluated between January 1, 1999, and March 31, 1999, and who required genetic counseling were retrospectively reviewed. The genetic risk assessment of the referring obstetrician was compared to the genetic risk assessment following counseling by a genetic counselor who used a questionnaire and a three-generation pedigree. The number of patients with additional genetic risk factors identified by the genetic counselor were recorded and compared by using the McNemar chi-square test. Group demographics and characteristics were evaluated. RESULTS: Among the 145 patients evaluated, 38% (n = 55) had additional genetic risk factors detected by the genetic counselor (P =.01). The maternal demographics and characteristics did not differ between the two groups. CONCLUSION: The practice of referring high-risk obstetric patients for genetic counseling improves the detection of identifiable genetic risk factors.

Defining the relationship between obstetricians and maternal-fetal medicine specialists.

OBJECTIVE: The purpose of this study was to determine how frequently general obstetricians refer pregnant patients to maternal-fetal medicine specialists in the presence of the clinical indications specified as appropriate for referral or consultation by the 1996 statement of the Society of Perinatal Obstetricians. STUDY DESIGN: A questionnaire was mailed to 400 randomly selected general obstetricians across the United States. The obstetricians were asked how often they refer their high-risk pregnant patients to maternal-fetal medicine specialists in the presence of (1) a need for diagnostic or therapeutic procedures, (2) medical/surgical disorders, (3) healthy gravid women with high-risk fetuses, and (4) conditions that necessitate admission for reasons other than delivery. Response categories for each individual procedure/high-risk condition included "always," "frequently," "infrequently," "never," and "not applicable." RESULTS: Overall, 55% of the responses indicated referral (always or frequently) to maternal-fetal medicine specialists for procedures or in the presence of high-risk conditions. More than 75% of the obstetricians always or frequently refer to maternal-fetal medicine specialists for most diagnostic/therapeutic procedures and for the following high-risk conditions: acute fatty liver, portal hypertension, pulmonary hypertension, transplantations, fetal hydrops, fetal anomaly/cytogenetic abnormality, fetal supraventricular tachycardia or congenital heart block, isoimmunization, and twin-to-twin transfusion syndrome. CONCLUSION: Most of the conditions for which >75% of the obstetricians refer to maternal-fetal medicine are rarely seen in practice. Comprehensive ultrasound examination is the only commonly encountered clinical situation that >75% of the general obstetricians refer to maternal-fetal medicine specialists.

A comparison of sonographic cervical parameters in predicting spontaneous preterm birth in high-risk singleton gestations.

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.

Revisiting sonographic abdominal circumference measurements: a comparison of outer centiles with established nomograms.

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.

Relationship among placenta previa, fetal growth restriction, and preterm delivery: a population-based study.

OBJECTIVE: To examine the independent contributions of prematurity and fetal growth restriction to low birth weight among women with placenta previa. METHODS: A population-based, retrospective cohort study of singleton live births in New Jersey (1989-93) was performed. Mother-infant pairs (n = 544,734) were identified from linked birth certificate and maternal and infant hospital discharge summary data. Women diagnosed with previa were included only if they were delivered by cesarean. Fetal growth, defined as gestational age-specific observed-to-expected mean birth weight, and preterm delivery (before 37 completed weeks) were examined in relation to previa. Severe and moderate categories of fetal smallness and large for gestational age were defined as observed-to-expected birth weight ratios below 0.75, 0.75-0.85, and over 1.15, respectively, all of which were compared with appropriately grown infants (observed-to-expected birth weight ratio 0.86-1.15). RESULTS: Placenta previa was recorded in 5.0 per 1000 pregnancies (n = 2744). After controlling for maternal age, education, parity, smoking, alcohol and illicit drug use, adequacy of prenatal care, maternal race, as well as obstetric complications, previa was associated with severe (odds ratio [OR] 1.37, 95% confidence interval [CI] 1.25, 1.50) and moderate fetal smallness (OR 1.24, 95% CI 1.17, 1.32) births. Preterm delivery was also more common among women with previa. Adjusted OR of delivery between 20-23 weeks was 1.81 (95% CI 1.24, 2.63), and 2.90 (95% CI 2.46, 3.42) for delivery between 24-27 weeks. OR for delivery by each week between 28 and 36 weeks ranged between 2.7 and 4.0. Approximately 12% of preterm delivery and 3.7% of growth restriction were attributable to placenta previa. CONCLUSION: The association between low birth weight and placenta previa is chiefly due to preterm delivery and to a lesser extent with fetal growth restriction. The risk of fetal smallness is increased slightly among women with previa, but this association may be of little clinical significance.

Fetal intracardiac echogenic foci: visualization depends on the orientation of the 4-chamber view.

OBJECTIVE: To compare the frequency of visualization of echogenic intracardiac foci in different cardiac views. METHODS: Women having ultrasonographic examinations between October 1997 and July 1998 were prospectively evaluated if a fetal echogenic intracardiac focus was seen in either ventricle. RESULTS: Echogenic intracardiac foci were seen in 89 fetuses in whom both the apical and lateral 4-chamber heart views were obtained. Eight-six fetuses (97%) had a single focus (83 in the left ventricle and 3 in the right ventricle), and 3 (3%) had 2 foci. Echogenic intracardiac foci were seen in the apical 4-chamber view in 89 (100%) and in the lateral 4-chamber view in only 26 (29%; P = .001). CONCLUSIONS: Echogenic intracardiac foci are not easily seen in the lateral 4-chamber view. Studies that suggest an increased risk of aneuploidy when echogenic foci are seen should specify the orientation of the 4-chamber view used.

Do maternal-fetal medicine practice characteristics influence high-risk referral decisions by general obstetrician-gynecologists?

OBJECTIVE: To determine whether the decision of the general obstetrician-gynecologist to refer high-risk obstetric patients depends on the type of practice of the maternal-fetal medicine (MFM) specialist. METHODS: A questionnaire was mailed to 935 general obstetrician-gynecologists who were asked whether the MFM specialist's practice characteristics would influence their decision to refer their high-risk obstetric patients. Potential MFM practice components presented in the survey included: MFM, high-risk obstetrics, low-risk obstetrics or general obstetrics and gynecology. RESULTS: A total of 140 (15%) general obstetrician-gynecologists responded, 110 of whom were practicing obstetrics. Of the practicing responders, 77% stated that they were more likely to refer their high-risk obstetric patients if the MFM specialist practiced only MFM and high-risk obstetrics; 69% were less likely to refer their patients when the MFM specialist, in addition to MFM, practiced general obstetrics; and 75% were less likely to refer their patients when the MFM specialist also practiced general obstetrics and gynecology. The MFM practice setting (university vs. community hospital vs. private practice), as well as the geographic location and years of practice of the respondents, did not influence the general obstetrician-gynecologists' decision to refer their high-risk obstetric patients. CONCLUSION: General obstetrician-gynecologists are more likely to refer high-risk obstetric patients if the MFM specialist practiced only MFM and high-risk obstetrics.

Ultrasonography of the fetal thyroid: nomograms based on biparietal diameter and gestational age.

OBJECTIVE: To describe gestational age-dependent and -independent nomograms for fetal thyroid size. METHODS: Two hundred fetuses were evaluated between 16 and 37 weeks' gestation in this cross-sectional study. RESULTS: Nomograms of fetal thyroid size were created by using the 5th, 10th, 50th, 90th, and 95th percentiles based on biparietal diameter and gestational age. A second-order polynomial fit for biparietal diameter and a linear fit for gestational age best described thyroid circumference measurements. Variations in thyroid circumference measurements increased with both larger biparietal diameter and advancing gestational age. There was no intraobserver or interobserver variability in thyroid circumference measurements (P > .20). CONCLUSIONS: Both biparietal diameter and gestational age serve as good predictors of fetal thyroid circumference. When the biparietal diameter is difficult to measure, gestational age can be used to assess thyroid size.

Placental abruption among singleton and twin births in the United States: risk factor profiles.

The authors performed a population-based epidemiologic study to evaluate and contrast risk factor profiles for placental abruption among singleton and twin gestations. Data were derived from linked US birth/infant death files for 1995 and 1996, comprising 7,465,858 singleton births and 193,266 twin births. The authors also evaluated effect modification between smoking and hypertension and the effect of a dose-response relation with number of cigarettes smoked daily on abruption risk. Abruption was recorded in 5.9 per 1,000 singleton births and 12.2 per 1,000 twin births. Risk factors for abruption among singleton and twin births, respectively, included preterm premature rupture of membranes (adjusted relative risks (RRs) = 4.89 and 2.01), eclampsia (RRs = 3.58 and 1.67), anemia (RRs = 2.23 and 2.33), hydramnios (RRs = 2.04 and 1.66), renal disorders (RRs = 1.54 and 2.56), and intrapartum fever (>100 degrees F) (RRs = 1.17 and 1.69). Chronic hypertension (RR = 2.38) and pregnancy-induced hypertension (RR = 2.34) were risk factors for abruption in singleton births but not in twin births. Number of cigarettes smoked daily demonstrated a dose-response trend for abruption risk in singletons and twins. Abruption was more likely to occur among smokers with chronic hypertension (RRs = 4.66 and 3.15) and eclampsia (RRs = 6.28 and 5.08). The authors conclude that abruption is twice as likely to occur in twins as in singletons with differing risk factor profiles. This suggests that abruption in twins may result from different pathophysiologic processes.

Outcome of prenatally diagnosed mild unilateral cerebral ventriculomegaly.

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.