William H. Barth

Late-Preterm Birth : Does the Changing Obstetric Paradigm Alter the Epidemiology of Respiratory Complications?

OBJECTIVE: To analyze the effect of gestational age, delivery mode, and maternal–fetal risk factors on rates of respiratory problems among infants born 34 or more weeks of gestation over a 9-year period. METHODS: Retrospective analysis of prospectively collected maternal and neonatal data on all inborn births at 34 or more weeks of gestation at a single tertiary care center for the years 1990–1998. Specific diagnostic criteria were concurrently applied by a single investigator. RESULTS: Over the 9-year period, late-preterm births increased by 37%, whereas births at more than 40 weeks decreased by 39%, resulting in a decrease in median age at delivery from 40 weeks to 39 weeks (P<.001). Respiratory problems occurred in 705 term or late-preterm infants (4.9%), with clinically significant morbidity (respiratory distress syndrome, meconium aspiration syndrome, or pneumonia) least common at 39–40 weeks of gestation. Respiratory morbidity was greater among infants born by cesarean delivery or complicated vaginal delivery compared with uncomplicated cephalic vaginal delivery. The rate of respiratory morbidity did not change over time (1990–1992 1.3%, 1993–1995 1.5%, 1996–1998 1.4%, P=.746). The etiologic fraction for respiratory morbidity did not change over time for infants 34–36 weeks but decreased twofold for infants born after 40 weeks. CONCLUSION: Over the 9-year study period, reduced respiratory morbidity associated with decreased births after 40 weeks were offset by the adverse respiratory effect of increased cesarean delivery rates and increased late-preterm birth rates. LEVEL OF EVIDENCE: III

The cost‐effectiveness of targeted or universal screening for vasa praevia at 18–20 weeks of gestation in Ontario

Please cite this paper as: Cipriano L, Barth W, Zaric G. The cost‐effectiveness of targeted or universal screening for vasa praevia at 18–20 weeks of gestation in Ontario. BJOG 2010;117:1108–1118.

Oxytocin labor stimulation of twin gestations: effective and efficient.

Objective To test the hypothesis that oxytocin labor stimulation of twin gestations is similar to that of singletons regarding dosage, time, complications, and ability to achieve vaginal delivery. Methods This retrospective investigation included 124 gravidas receiving oxytocin for augmentation or induction of labor. Sixty-two women with twin gestations were matched by parity, cervical dilation at initiation of oxytocin, gestational age, oxytocin dosage regimen, and indications for oxytocin to controls with singleton pregnancies. Outcome variables included maximum dosage of oxytocin, incidence of hyperstimulation and fetal heart rate (FHR) abnormalities, time from oxytocin to delivery, cesarean deliveries, and maternal and neonatal outcomes. Statistical analysis was done using McNemar test, paired t test, and Wilcoxon signed-rank test for paired samples. Results Women with twin pregnancies and those with singletons responded similarly regarding maximum oxytocin dosage (21 ± 1.5 and 18 ± 2.4 mU/minute, respectively, P = .1), time from oxytocin to delivery (7.0 ± 0.8 and 6.7 ± 0.6 hours, respectively, P = .88), and successful vaginal delivery (90% and 90%, respectively). Oxytocin stimulation of twins resulted in fewer interruptions of the infusion for FHR abnormalities (5% compared with 26%, odds ratio [OR] 0.27, 95% confidence interval [CI] 0.16, 0.47) and hyperstimulation (6% compared with 18%, OR 0.19, 95% CI 0.36, 0.99). Conclusion Twin gestation has no adverse impact on the effectiveness or efficiency of oxytocin labor stimulation. Twin pregnancy seems to be associated with fewer side effects.

Cardiac surgery in pregnancy.

The need for cardiac surgery during pregnancy is rare. Only 1% to 4% of pregnancies are complicated by maternal cardiac disease and most of these can be managed with medical therapy and lifestyle changes. On occasion, whether owing to natural progression of the underlying cardiac disease or precipitated by the cardiovascular changes of pregnancy, cardiac surgical therapy must be considered. Cardiac surgery is inherently dangerous for both, the mother and fetus with mortality rates near 10% and 30%, respectively. For some conditions, percutaneous cardiac intervention offers effective therapy with far less risk to the mother and her fetus. For others, cardiac surgery, including procedures that mandate the use of cardiopulmonary bypass, must be entertained to save the life of the mother. Given the extreme risks to the fetus, if the patient is in the third trimester, strong consideration should be given to delivery before surgery involving cardiopulmonary bypass. At earlier gestational ages when this is not feasible, modifications to the perfusion protocol including higher flow rates, normothermic perfusion, pulsatile flow, and the use of intraoperative external fetal heart rate monitoring should be considered.

Persistent occiput posterior.

Persistent occiput posterior (OP) is associated with increased rates of maternal and newborn morbidity. Its diagnosis by physical examination is challenging but is improved with bedside ultrasonography. Occiput posterior discovered in the active phase or early second stage of labor usually resolves spontaneously. When it does not, prophylactic manual rotation may decrease persistent OP and its associated complications. When delivery is indicated for arrest of descent in the setting of persistent OP, a pragmatic approach is suggested. Suspected fetal macrosomia, a biparietal diameter above the pelvic inlet or a maternal pelvis with android features should prompt cesarean delivery. Nonrotational operative vaginal delivery is appropriate when the maternal pelvis has a narrow anterior segment but ample room posteriorly, like with anthropoid features. When all other conditions are met and the fetal head arrests in an OP position in a patient with gynecoid pelvic features and ample room anteriorly, options include cesarean delivery, nonrotational operative vaginal delivery, and rotational procedures, either manual or with the use of rotational forceps. Recent literature suggests that maternal and fetal outcomes with rotational forceps are better than those reported in older series. Although not without significant challenges, a role remains for teaching and practicing selected rotational forceps operations in contemporary obstetrics.

Race, cardiovascular reactivity, and preterm delivery among active-duty military women.

Background: Rates of preterm delivery in the United States are higher in black women compared with whites. In this study, we examined cardiovascular reactivity and risk of preterm delivery among black and white military women. Methods: We recruited a total of 500 black and white active-duty military women from the prenatal clinic at a large military installation, interviewing them early in pregnancy and again at 28 weeks of gestation. A subgroup of women underwent a computerized stress test to determine cardiovascular reactivity assessed as increases in heart rate and blood pressure compared with measurements taken before the stress test. Results: Despite a relatively low overall risk of preterm delivery (8.2%), we found the same 2-fold racial disparity reported in other populations (hazard ratio for preterm delivery in black women vs whites = 2.30; 95% confidence interval = 1.24–4.27). The disparity is present in all military ranks and is largest for medically indicated preterm deliveries. Among the 313 subjects who participated in the computerized stress testing, blacks exhibited more cardiac reactivity than whites. In black subjects only, a 1-mm increase in diastolic blood pressure reactivity was associated with 1.1 a day earlier delivery (−0.17 weeks). A similar trend was seen with heart rate. Conclusions: Autonomic dysfunction after exposure to stressors may play a role in the timing of delivery among black women.

The pharmacokinetics of oxytocin as they apply to labor induction.

OBJECTIVE Our purpose was to determine the relationship among plasma oxytocin levels, metabolic clearance rate of oxytocin, and uterine activity in gravid women undergoing labor induction. STUDY DESIGN Ten women receiving oxytocin for labor induction and agreeing to participate had blood sampled before initiation of oxytocin and at different levels of uterine pressure. Samples were analyzed with 200 microliter extracts from 1 ml of plasma with an oxytocin radioimmunoassay. The intraassay coefficient of variation was < 3%. Sensitivity of the assay was 1.5 pg/ml. Pharmacokinetic parameters including plasma levels and metabolic clearance rates were calculated. Data were analyzed with the paired t test and linear and logistic regression. RESULTS Mean oxytocin levels and metabolic clearance rates were 26.6 pg/ml and 7.97 ml/min. There was no correlation between changes in oxytocin level and metabolic clearance rate. Increases in infusion rates were correlated with increases in oxytocin levels (r = 0.71, p < 0.001). Cervical dilatation and uterine contraction pressures did not correlate with oxytocin levels. CONCLUSION Peripheral plasma levels of oxytocin may not accurately reflect uterine activity or progress in labor. Plasma levels of oxytocin may merely reflect the rate of oxytocin infusion.

Transvaginal cervical length scans to prevent prematurity in twins: a randomized controlled trial

BACKGROUND Twin pregnancies are associated with an increased risk of perinatal morbidity and mortality primarily due to spontaneous preterm deliveries. The mean gestational age for delivery is 35.3 weeks and twins account for 23% of preterm births <32 weeks. A number of strategies have been proposed to prevent preterm deliveries: tocolytics, bed rest, hospitalization, home uterine activity monitoring, cerclage, and most recently, progesterone. Unfortunately, none have proven effective. Recent metaanalyses and reviews suggest that transvaginal cervical length (TVCL) ultrasound in the second trimester is a powerful predictor of preterm birth among asymptomatic women. Indeed, TVCL has the highest positive and negative predictive values for determining the risk of spontaneous preterm delivery in twin pregnancies. It follows that TVCL assessment may allow identification of a subset of twin pregnancies that re better candidates for interventions intended to prevent prematurity. OBJECTIVE We sought to determine whether use of TVCL prolongs gestation in twin pregnancies. STUDY DESIGN This is a multicenter, randomized, controlled trial of 125 dichorionic or monochorionic/diamniotic twin pregnancies without prior preterm birth <28 weeks. The study group (n = 63) had TVCL and digital exams monthly from 16-28 weeks and were managed with a standard algorithm for activity restriction and cerclage. The control group (n = 62) had monthly digital cervical examinations but no routine TVCL ultrasound examinations. The primary outcome was gestational age at delivery. Secondary outcomes included percentage of deliveries <35 weeks, and maternal and neonatal outcomes. RESULTS The mean gestational age at delivery was 35.7 weeks (95% confidence interval [CI], 35.2-36.2) among those managed with TVCL and 35.5 weeks (95% CI, 34.7-36.4) among the control patients. The Kaplan-Meier estimates of deliveries <38 weeks were not significantly different between groups. This was true whether we compared curves with a log-rank test (P = .67), Breslow test (P = .67), or Tarone-Ware test (P = .64). The percentage of deliveries <35 0/7 weeks did not differ: 27.4% for subjects managed with routine TVCL and 28.6% for control subjects (relative risk, 0.96; 95% CI, 0.60-1.54). Our study had an 80% power to detect a 12-day difference in the gestational age at delivery with 95% confidence. CONCLUSION The overall mean length of gestation and the percentage of women delivering <35 weeks did not differ between twin gestations managed with TVCL and digital exams monthly from 16-28 weeks with a standard algorithm for activity restriction and cerclage and controls who had monthly digital cervical examinations but no routine TVCL. Routine second-trimester transvaginal ultrasound assessment of cervical length is not associated with improved outcomes when incorporated into the standard management of otherwise low-risk twin pregnancies.

In Vivo Quantification of Placental Insufficiency by BOLD MRI: A Human Study

Fetal health is critically dependent on placental function, especially placental transport of oxygen from mother to fetus. When fetal growth is compromised, placental insufficiency must be distinguished from modest genetic growth potential. If placental insufficiency is present, the physician must trade off the risk of prolonged fetal exposure to placental insufficiency against the risks of preterm delivery. Current ultrasound methods to evaluate the placenta are indirect and insensitive. We propose to use Blood-Oxygenation-Level-Dependent (BOLD) MRI with maternal hyperoxia to quantitatively assess mismatch in placental function in seven monozygotic twin pairs naturally matched for genetic growth potential. In-utero BOLD MRI time series were acquired at 29 to 34 weeks gestational age. Maps of oxygen Time-To-Plateau (TTP) were obtained in the placentas by voxel-wise fitting of the time series. Fetal brain and liver volumes were measured based on structural MR images. After delivery, birth weights were obtained and placental pathological evaluations were performed. Mean placental TTP negatively correlated with fetal liver and brain volumes at the time of MRI as well as with birth weights. Mean placental TTP positively correlated with placental pathology. This study demonstrates the potential of BOLD MRI with maternal hyperoxia to quantify regional placental function in vivo.

Case 7-2009: A Pregnant Woman with a Large Mass in the Fetal Oral Cavity

From the Department of Otolaryngology, Massachusetts Eye and Ear Infirmary (C.J.H.); the Departments of Maternal and Fetal Medicine (W.H.B.), Anesthesia and Critical Care (C.J.C., M.A.A.), Radiology (P.E.G.), and Pathology (J.T.G.), Massachusetts General Hospital; and the Departments of Otolaryngology (C.J.H.), Obstetrics, Gynecology, and Reproductive Biology (W.H.B.), Anesthesia and Critical Care (C.J.C., M.A.A.), Radiology (P.E.G.), and Pathology (J.T.G.), Harvard Medical School ― all in Boston.