Intrapartum cesarean delivery in nulliparas: risk factors compared by two analytical approaches.

OBJECTIVE: To determine risk factors for cesarean delivery in nulliparas at labor admission. STUDY DESIGN: Nulliparas with live-born, singleton gestations ⩾37 weeks in spontaneous or induced labor were analyzed from the Consortium on Safe Labor database in a retrospective observational study. Classification and regression tree (CART) and multivariate logistic regression analysis determined risk factors for cesarean delivery. RESULT: Of the 66 539 nulliparas, 22% had a cesarean delivery. In the CART analysis, the first cervical dilation exam was the first branch followed by body mass index (BMI). Cesarean deliveries occurred in 45%, 25%, 14% and 10% of deliveries at <1, 1 to 3, 4 and ⩾5 cm dilated, respectively. The BMI influence was most evident in the <1 cm dilation category with 26% of BMI <25 kg m(-2) and 66% of BMI ⩾40 kg m(-2) having a cesarean delivery. The fewest cesarean deliveries (5%) occurred in those ⩾5 cm and BMI <25 kg m(-2). In the multivariate regression analysis, first cervical dilation exam <1 cm (odds ratio (OR) 5.1, 95% confidence interval (CI): 4.5 to 5.7; reference ⩾5 cm) and BMI ⩾40 kg m(-2) (OR 5.1, 95% CI: 4.6 to 5.7; reference BMI <25.0 kg m(-2)) had the highest odds for cesarean delivery. CONCLUSION: Cervical dilation on admission followed by BMI were the two most important risk factors for cesarean delivery identified in both CART and multivariate regression analysis.

OS015. What is the optimal time for delivery in women with gestationalhypertension?

INTRODUCTION: There is conflicting evidence regarding the treatment of women with gestational hypertension (GHTN). OBJECTIVES: To assess the optimal timing of delivery for women with GHTN by quantifying the risks of adverse maternal and fetal outcomes associated with ongoing pregnancy and with induction of labor at each gestational week 36-41 completed weeks. METHODS: The Consortium on Safe Labor electronic database from 19 hospitals across the US with 228,668 deliveries 2002-2008 was used to extract data on gravidas with GHTN, diagnosis assigned at delivery admission, using standard definitions. We only considered the first pregnancy to avoid intra-person correlation. Pregnancies complicated by diabetes mellitus, cardiac, pulmonary, or renal disease were excluded. The week-specific rates of maternal and neonatal morbidity/mortality (M/M) were calculated following induction of labor. Maternal outcomes included serious morbidity (composite defined as any of: ICU admission, abruption, large blood loss (>0.5L SVD, >1.0L CS), postpartum HTN) and mortality. Neonatal outcomes included SGA (⩽10th %tile), serious morbidity (composite defined as any of: seizures, severe respiratory morbidity or 5-min Apgar score ⩽3) and mortality. Pointwise 95% CI were calculated around each of these gestational age-specific rates. Statistical analyses were performed using FREQ, GLM and LOGISTIC procedures in SAS 9.2. RESULTS: Following induction of labor, the rate of maternal M/M reached a nadir of 89.6 per 1000 live births [95% CI 67.8,111.5], at 38-38 6/7 weeks gestation, while the rate of neonatal M/M fell to 10.5 per 1000 live births [95% CI 2.8,18.2], at 39-39 6/7 weeks. The rate of SGA ⩽10th ‰decreased sharply between 36 and 37 weeks from 109.7 [95% CI 69.9,149.5], to 52.0 [95% CI 31.3,72.7]. CONCLUSION: In women with GHTN, induction of labor prior to 38weeks results in greater maternal M/M, but for the neonate induction at 39weeks results in lowest M/M.

OS030. Hypertension and labor duration: Does it take longer?

INTRODUCTION: Hypertensive disease in pregnancy carries higher maternal and fetal morbidity and mortality and often requires labor induction to minimize risk. It was previously taught that preeclampsia was associated with a more rapid progression through all stages of labor, while there is a paucity of data in other hypertensive categories. One investigation in preeclamptic women demonstrated that labor progress was prolonged with increased risk for cesarean delivery. OBJECTIVES: To study labor progression in induced nulliparas at term with hypertensive diseases in pregnancy. METHODS: Retrospective cohort study using data from the Consortium on Safe Labor; a multicenter project that abstracted labor and delivery information from electronic medical records in 19 hospitals across the US. A total of 32,276 women with singleton term gestation, induced labor, and vertex presentation were studied. Hypertensive women were grouped into 4 separate categories: chronic hypertension (cHTN), gestational hypertension (gHTN), preeclampsia (PreE) and superimposed preeclampsia (SIPreE) and compared to controls (no hypertensive disorder). For the first stage of labor, Interval-censored regression analysis was used to estimate median and 95th% duration of labor, centimeter by centimeter and from 4-10cm. RESULTS: Significant differences were noted in demographics between each group and controls including age, race, labor admission body mass index, gestational age at delivery, comorbidities, and admission cervical dilation (P<0.01 for all comparisons to the control group). As noted in the table, women with cHTN and SIPreE had a longer first stage of labor, gHTN had a shorter first stage of labor, and labor length was similar in PreE compared to controls. Second stage of labor was longer (5-41min) with epidural and varied among groups; however, the clinical significance is limited. 95th% for progression from 4-10cm in cHTN, SIPreE and gHTN were 27.4, 28.2 and 16.5h respectively (controls 20.1h) (). CONCLUSION: In nulliparas induced at term with hypertensive disease, labor progression in the first and second stage varies from controls. gHTN women have the shortest first stage of labor while PreE gravidas have labor patterns similar to controls. As cHTN and SIPreE women have a longer first stage, allowing labor to continue for a longer period in these gravidas may contribute to a reduced rate of cesarean delivery in the US, but will require further investigation.

PP028. To assess maternal and neonatal outcomes of women on an antihypertensive agent with gestational hypertension, chronic hypertension or preeclampsia.

INTRODUCTION: There is a lack of evidence regarding antihypertensive medicine use in pregnancy. OBJECTIVES: To compare maternal and neonatal outcomes of women on an antihypertensive agent with gestational hypertension (GHTN), chronic hypertension (CHTN) and preeclampsia (preE). METHODS: The Consortium on Safe Labor electronic database from 19 hospitals across the US with 228,668 deliveries during 2002-2008 was used to extract data on gravidas with GHTN, CHTN, and preE on a calcium channel blocker, methyldopa, or beta blocker. Univariate and multivariate analyses were performed. RESULTS: There were 637 women on beta blockers, 207 on calcium channel blockers, 249 on Methyldopa, and 6869 women with hypertension on no agent (control group). Women on beta blockers had an increased risk of ICU admission, OR 3.74 (95% CI 1.8-7.6). Risk of thrombosis was increased in women on beta blockers, OR 3.6 (95% CI 1.4-9.2) and calcium channel blockers, OR 10.6 (95% CI 3.8-29.2). There was no increased risk of small for gestational age babies. There was a small, increased risk of NICU admission for babies of women on calcium channel blockers, OR 1.7 (95% CI 1.2-2.6) and methyldopa, OR 1.9 (95% CI 1.4-2.7). CONCLUSION: Beta and calcium channel blocker use was associated with significant risks of morbidity compared to Methyldopa use by gravid women with hypertensive disease.

Low-molecular-weight heparin in pregnancy: peripartum bleeding complications.

OBJECTIVE: To compare bleeding complications in pregnant patients treated with low-molecular-weight heparin (LMWH) to untreated controls. STUDY DESIGN: A case-control study of patients from 2001 to 2005 who received prophylactic or therapeutic doses of LMWH during pregnancy was carried out. Indications for LMWH included current or prior thromboembolism, thrombophilia, or heart valve replacement. Controls were chosen in a 2:1 ratio to cases, matched for delivery route, and selected as the next two consecutive deliveries. The primary outcome was postpartum hemorrhage (PPH). Odds ratios (ORs) were calculated with 95% confidence intervals (CIs). RESULTS: Forty-nine women treated with LMWH delivered 55 infants. Current or prior thromboembolic disease was the anticoagulation indication in 15/55 (27.3%) and 26/55 (47%) of pregnancies, respectively. There were more obese gravidas (OR 3.91, CI 1.70 to 9.09) and labor induction was more common in the LMWH group, 25/55 (45%) vs 29/110 (26%), P=0.01. There was no difference in estimated blood loss (295.7+/-145.7 vs 308.6+/-111.9 cm(3), P=0.62 vaginal; 687.5+/-251.8 vs 765.0+/-313.2 cm(3), P=0.34 cesarean), PPH (6/55, 11% vs 9/110, 8.2% OR 1.37, CI 0.16 to 11.5) or transfusion (3/55, 5.4% vs 4/110, 3.6% OR 1.50, CI 0.3 to 7.48) between the cases and controls. There were two cases of postpartum pulmonary emboli, one with a maternal mortality. CONCLUSION: Bleeding complications, including PPH and transfusion, in patients treated with LMWH during pregnancy were not increased when compared to normal controls matched for delivery route.

Failed vaginal birth after a cesarean section: how risky is it? I. Maternal morbidity.

OBJECTIVE: Our purpose was to determine the maternal risks associated with failed attempt at vaginal birth after cesarean compared with elective repeat cesarean delivery or successful vaginal birth after cesarean. STUDY DESIGN: From 1989 to 1998 all patients attempting vaginal birth after cesarean and all patients undergoing repeat cesarean deliveries were reviewed. Data were extracted from a computerized obstetric database and from medical charts. The following three groups were defined: women who had successful vaginal birth after cesarean, women who had failed vaginal birth after cesarean, and women who underwent elective repeat cesarean. Criteria for the elective repeat cesarean group included no more than two previous low transverse or vertical incisions, fetus in cephalic or breech presentation, no previous uterine surgery, no active herpes, and adequate pelvis. Predictor variables included age, parity, type and number of previous incisions, reasons for repeat cesarean delivery, gestational age, and infant weight. Outcome variables included uterine rupture or dehiscence, hemorrhage >1000 mL, hemorrhage >2000 mL, need for transfusion, chorioamnionitis, endometritis, and length of hospital stay. The Student t test and the chi(2) test were used to compare categoric variables and means; maternal complications and factors associated with successful vaginal birth after cesarean were analyzed with multivariate logistic regression, allowing odds ratios, adjusted odds ratios, 95% confidence intervals, and P values to be calculated. RESULTS: A total of 29,255 patients were delivered during the study period, with 2450 having previously had cesarean delivery. Repeat cesarean deliveries were performed in 1461 women (5.0%), and 989 successful vaginal births after cesarean delivery occurred (3.4%). Charts were reviewed for 97.6% of all women who underwent repeat cesarean delivery and for 93% of all women who had vaginal birth after cesarean. Vaginal birth after cesarean was attempted by 1344 patients or 75% of all appropriate candidates. Vaginal birth after cesarean was successful in 921 women (69%) and unsuccessful in 424 women. Four hundred fifty-one patients undergoing cesarean delivery were deemed appropriate for vaginal birth after cesarean. Multiple gestations were excluded from analysis. Final groups included 431 repeat cesarean deliveries and 1324 attempted vaginal births after cesarean; in the latter group 908 were successful and 416 failed. The overall rate of uterine disruption was 1.1% of all women attempting labor; the rate of true rupture was 0.8%; and the rate of hysterectomy was 0.5%. Blood loss was lower (odds ratio, 0.5%; 95% confidence interval, 0.3-0.9) and chorioamnionitis was higher (odds ratio, 3.8%; 95% confidence interval, 2.3-6.4) in women who attempted vaginal births after cesarean. Compared with women who had successful vaginal births after cesarean, women who experienced failed vaginal births after cesarean had a rate of uterine rupture that was 8.9% (95% confidence interval, 1.9-42) higher, a rate of transfusion that was 3.9% (95% confidence interval, 1.1-13.3) higher, a rate of chorioamnionitis that was 1.5% (95% confidence interval, 1.1-2.1) higher, and a rate of endometritis that was 6.4% (95% confidence interval, 4.1-9.8) higher. CONCLUSION: Patients who experience failed vaginal birth after cesarean have higher risks of uterine disruption and infectious morbidity compared with patients who have successful vaginal birth after cesarean or elective repeat cesarean delivery. Because actual numbers of morbid events are small, caution should be exercised in interpreting results and counseling patients. More accurate prediction for safe, successful vaginal birth after cesarean delivery is needed.

Cervical length at 16-22 weeks' gestation and risk for preterm delivery.

OBJECTIVE: To determine whether cervical length, as measured by transvaginal sonogram in asymptomatic gravidas at 16-22 weeks, is associated with risk of spontaneous preterm delivery. METHODS: In a prospective observational study in an unselected urban tertiary care population, cervical length was measured by transvaginal ultrasound during routine anatomic surveys in 760 gravidas at 16 0/7 to 22 6/7 weeks. The predictor variable was cervical length and the outcome variable was gestational age at delivery. Care providers were not masked to the results. Spontaneous preterm delivery was analyzed as before 37, 35, and 32 weeks. Shortened cervical length was defined by the tenth, fifth, and two and a half percentiles for our population. Yates-corrected chi(2) was used to evaluate the significance on univariate analysis of the relative risk (RR) and 95% confidence intervals (CI). Multiple logistic regression analysis was used to control for background variables in evaluating the probability of preterm delivery at less than 35 weeks. Sensitivity, specificity, positive and negative predictive values also were calculated. RESULTS: Cervical lengths were normally distributed (mean 38.5 +/- 8.0 mm at 19.9 +/- 1.5 weeks) independent of gestational age at measurement, and the tenth, fifth, and two and a half percentiles were 30, 27, and 22 mm, respectively. Eighty-five women delivered before 37 weeks, 51 before 35 weeks, and 27 before 32 weeks. Relative risks (95% CI) for spontaneous preterm delivery before 37 weeks were 3.8 (2.6, 5.6), 5.4 (3.3, 9.0), and 6.3 (3.0, 13.0) for the tenth, fifth, and two and a half percentiles, respectively; RRs for before 35 weeks were 4.5 (2.9, 6.9), 7.5 (4.5, 12.5), and 7.8 (3.6, 16.7); and for before 32 weeks were 5.2 (3.3, 8.3), 9.7 (5.8, 16.1), and 8.4 (3.6, 19.9), respectively. Multiple logistic regression analysis confirmed that cervical length was a significant predictor of preterm birth before 35 weeks, and that paras had a 43% greater risk compared with nulliparas. Sensitivity ranged from 13-44%, specificity 90-99%, positive predictive value 15-47%, and negative predictive value 80-98%. CONCLUSION: Transvaginal measurement of cervical length during routine ultrasound at 16-22 weeks' gestation in asymptomatic gravidas might help identify women at risk for spontaneous preterm delivery.

Short cervical length by ultrasound and cerclage.

OBJECTIVE: To determine whether gravidas with short cervical length on endovaginal ultrasound examination, not in preterm labor, who underwent cervical cerclage have better outcomes compared with those with no cerclage. METHODS: This is an observational study in which data were collected prospectively on women who had ultrasound endovaginal cervical length measurement and were not in preterm labor. The subgroup of women who were < or = 26 weeks' at cervical measurement was analyzed separately. Short cervix was defined as < or = 30 mm. After delivery, charts were reviewed for management and outcomes, performed at the discretion of the attending obstetrician. Two study groups were defined: those with cerclage and those with no cerclage. Predictor variables were cerclage and cervical lengths. Outcome variables were birth weight, gestational age at delivery, and neonatal outcomes. Data were analyzed using the chi-squared, Fisher's exact, and Student's t-tests, a p value of < 0.05 was considered to be significant. RESULTS: A total of 85 patients with cervical lengths of < or = 30 mm were identified; of these 43 had cerclage, and 42 did not. The latter had bedrest, tocolytics, or no intervention. Indications for cervical length measurement were similar in both groups, as were age, insurance status, cervical measurements, preterm premature rupture of membranes, and mode of delivery. The mean gestational age at delivery and birth weight in the cerclage group (34.0 +/- 5.4 weeks'; 2530 +/- 905 gm) were greater than in the no cerclage group (32.0 +/- 6.0 weeks', 2084 +/- 1085 gm, p values of < 0.04 and < 0.04, respectively). Analysis for the subgroup of women who were < or = 26 weeks at first measurement revealed similar results. The relative risk for delivering at < 30 weeks' gestation, for incrementally shorter cervices, was less in the cerclage group. CONCLUSION: Cerclage in gravidas with short cervix measured by endovaginal ultrasound, not in preterm labor, may be associated with neonates of greater gestational age and birth weight, with fewer of these parturients delivering before 30 weeks' gestation. A prospective randomized trial of treatment modalities for asymptomatic shortened cervix is needed.

Reducing unnecessary coagulation testing in hypertensive disorders of pregnancy.

OBJECTIVE: To estimate the magnitude of laboratory testing for hypertension in pregnancy and determine whether abnormalities in prothrombin time (PT), activated partial thromboplastin time (aPTT), and fibrinogen can be predicted by results of common, less expensive tests. MATERIALS AND METHODS: Laboratory records were searched and charts were reviewed to identify gravidas tested for hypertension and to exclude conditions producing coagulopathy. Contingency tables were constructed to assess the ability of the platelet count, lactate dehydrogenase, and transaminases to predict coagulation test results. RESULTS: Preliminary data on 73 gravidas found that a platelet count plus a lactate dehydrogenase test best predicted coagulation abnormalities. Results on another 732 gravidas indicated that coagulation tests were obtained in about 30%. No patient had a PT greater than 18 seconds, two had an aPTT greater than 40 seconds, and three had fibrinogen levels less than 200 mg/dL. The combination of a normal platelet count plus a normal lactate dehydrogenase had a negative predictive value of 100% for clinically significant abnormalities of PT and aPTT, and 99% for significant abnormalities of fibrinogen. CONCLUSIONS: Substantial coagulation testing was done on gravidas evaluated for a hypertensive disorder even though the prevalence of clinically significant abnormalities was low. Laboratory evaluation of patients suspected of having preeclampsia need not include a PT, aPTT, or fibrinogen test when there is no evidence of bleeding or of a condition that could produce coagulopathy and when the platelet count and lactate dehydrogenase level are both normal.

A modified definition for peripartum cardiomyopathy and prognosis based on echocardiography.

The diagnosis of peripartum cardiomyopathy is one of exclusion, made after careful search for an underlying cause. Research in this area is compromised by the reliance of some on clinical criteria alone without strict echocardiographic criteria. This article argues for uniform criteria that define peripartum cardiomyopathy, similar to the criteria for idiopathic dilated cardiomyopathy set forth by a National Heart, Lung, and Blood Institute-sponsored workshop and proposes that the new definition include heart failure within the last month of pregnancy or 5 months postpartum; absence of preexisting heart disease; no determinable etiology, the traditional definition; and strict echocardiographic criteria of left ventricular dysfunction: ejection fraction less than 45%, or M-mode fractional shortening less than 30%, or both, and end-diastolic dimension more than 2.7 cm/m2. Mortality from peripartum cardiomyopathy remains high, 25-50%, and a recent review related long-term prognosis to echocardiographic measures of left ventricular chamber dimension and function at diagnosis and recovery. We describe a modified pharmacologic echocardiographic stress test that might be useful in determining left ventricular contractile reserve in women believed to be recovered by routine echocardiographic studies. The test reproduces hemodynamic stress akin to pregnancy, and the data might be useful when counseling women on future childbearing. Women who respond with reduced cardiac reserve might be advised to avoid pregnancy.

Group B streptococcus: to culture or not to culture?

OBJECTIVE: To determine if universal Group B Streptococcus (GBS) culturing and antibiotic prophylaxis of obstetric patients decreased the incidence of neonatal early-onset GBS sepsis and mortality and maternal chorioamnionitis. STUDY DESIGN: A time series observational study was conducted to compare the cohort of all obstetric patients delivering at the University of Chicago neonatal center from January 1989 through December 1993, before a GBS surveillance policy existed, with the cohort delivering January 1994 through December 1996, after initiation of a GBS policy. Included in the policy were universal GBS cultures at 28 weeks' gestation, antibiotic prophylaxis at the time of labor for all those with positive cultures and for all with risk factors of preterm delivery, preterm premature rupture of membranes, prolonged rupture of membranes greater than 18 hours, and a previous child affected by GBS or maternal fever in labor. Predictor variables were GBS culturing and antibiotic usage; outcome variables were incidence of GBS sepsis and mortality in the neonates and maternal chorioamnionitis. chi-squared and Fisher exact analyses were used with p < 0.05 being significant. RESULTS: Before the GBS policy, there were 16,272 deliveries with a 2.24/1000 deliveries rate of early-onset GBS sepsis (n = 35); after initiating the GBS policy, 9130 deliveries occurred with an early-onset GBS sepsis rate of 2.29/1000 (n = 20). Early-onset GBS sepsis case fatality rates before and after initiation of the policy were 14.3% and 0%, respectively (p = 0.09). Antibiotic use almost doubled (relative risk = 1.84; confidence interval, 1.74 to 1.93, p < 0.001) over the two time periods, and the relative risk of chorioamnionitis decreased to 0.95 (confidence interval, 0.73 to 0.99, p = 0.04). CONCLUSION: Despite universal GBS culturing and very liberal use of antibiotics in labor, we were unable to effect a statistically significant change in the rate of early-onset GBS sepsis or mortality, and there was only a slightly decreased chorioamnionitis rate.

Pregnancy in a nonimmunosuppressed transplant recipient.

A 30-year-old woman with a living related six-antigen-matched kidney allograft conceived 10 years posttransplantation. She had discontinued her immunosuppression medications 3 years previously. The allograft functioned well throughout gestation, which was complicated by preeclampsia, leading to induction at 35 weeks and delivery of a 2,175-g male.

Cervical ripening with prostaglandin gel and hygroscopic dilators.

OBJECTIVE: To study the effectiveness and morbidity of adding hygroscopic cervical dilators to prostaglandin gel for cervical ripening and labor induction. STUDY DESIGN: Patients of at least 34 weeks' gestation with a medical indication for induction of labor and with a modified Bishop score of 5 or less were randomized to receive either prostaglandin gel or prostaglandin gel with hygroscopic cervical dilators. Primary outcomes were time to delivery, change in cervical score, and infection. Secondary outcomes included cesarean delivery rate and deliveries before 24 hours of induction. Continuous variables were analyzed by Wilcoxon sum rank test and categorical data by chi-square or Fisher exact test, with P < 0.05 being significant. RESULTS: Seventeen patients were randomized to intracervical prostaglandin alone and 23 patients received intracervical prostaglandin plus hygroscopic dilators. No demographic differences were noted between the groups. After six hours of ripening, the combined group achieved a greater change in Bishop score (3.6 vs. 2.1, P = 0.007) and tended to have a shorter induction time (21.7 vs. 26.4 hours, P = 0.085). The combined therapy group had a higher infection rate than the prostaglandin-only group (59% vs. 12%, P = 0.003). CONCLUSION: Combining cervical dilators with prostaglandin gel provides more effective cervical ripening and a more rapid induction to delivery interval than prostaglandin alone but with a significant and prohibitive rate of infection.

Serial assessment of the cardiovascular system in normal pregnancy. Role of arterial compliance and pulsatile arterial load.

BACKGROUND: Temporal changes in systemic arterial compliance and wave propagation properties (pulsatile arterial load) and their role in ventricular-systemic arterial coupling during gestation have not been explored. Noninvasive methods combined with recently developed mathematical modeling techniques were used to characterize vascular and left ventricular (LV) mechanical adaptations during normal gestation. METHODS AND RESULTS: Fourteen healthy women were studied at each trimester of pregnancy and again postpartum. Experimental measurements included instantaneous aortic pressure (subclavian pulse tracings) and flow (aortic Doppler velocities) and echocardiographic imaging of the LV. A small increase in LV muscle mass and end-diastolic chamber dimension occurred by late gestation, with no significant alterations in myocardial contractility. Cardiac output increased and the steady component of arterial load (total vascular resistance) decreased during pregnancy. Several changes in pulsatile arterial load were noted: Global arterial compliance increased (approximately 30%) during the first trimester and remained elevated thereafter. The magnitude of peripheral wave reflections at the aorta was reduced. The mathematical model-based analysis revealed that peripheral wave reflections at the aorta were delayed and that both conduit and peripheral vessels contributed to the increased arterial compliance. Finally, coordinated changes in the pulsatile arterial load and LV properties were responsible for maintaining the efficiency of LV-to-arterial system energy transfer. CONCLUSIONS: The rapid time course of compliance changes and the involvement of both conduit and peripheral vessels are consistent with reduced vascular tone as being the main underlying mechanism. The pulsatile arterial load alterations during normal pregnancy are adaptive in that they help to accommodate the increased intravascular volume while maintaining the efficiency of ventricular-arterial coupling and diastolic perfusion pressure.

Does chorionic villus sampling compromise fetal umbilical blood flow?

A possible association of limb reduction defects with chorionic villus sampling (CVS) may be related to compromised umbilical blood flow from the trauma of the procedure. We hypothesized that because CVS may disrupt or compromise umbilical blood flow to the fetus, either by vasoconstriction, bradycardia, or emboli, we would detect these changes using Doppler velocimetry. A cohort of 21 consecutive consenting patients undergoing first-trimester elective CVS for prenatal diagnosis were entered into a prospective longitudinal study. Colour flow Doppler velocimetry was performed on fetal umbilical arterial blood flow immediately before and after CVS to measure the pulsatility index, fetal heart rate, per cent flow time, and maximum flow velocity. Measurements were obtained from three consecutive cardiac cycles in three different umbilical segments and averaged. Potentially confounding variables also recorded included gestational age, method of CVS, number of passes, number of aspirations, placental location, tissue sample size, and operator. Umbilical velocimetry values before and after CVS were compared using the paired t-test and showed no statistically significant differences. No differences were found when data were analysed by gestational age, sample size, method, number of aspirations, placental location, or operator. We were unable to detect any significant change in fetal umbilical arterial blood flow velocimetry or heart rate after performing CVS. Umbilical blood flow does not appear to be routinely compromised by CVS.

Reducing the frequency of low birth weight in the United States.

We sought to determine by what amount the frequency of low birth weight (LBW) could be reduced by eliminating its known, preventable risk factors. Based on the prevalence of risk factors such as cigarette smoking (exposure) in a population, and the degree of association (relative risk) between the risk factors and the outcome of LBW, we estimated the percentage of LBW in the United States attributable to the risk factors (population-attributable risk percentage). We found the following associations with known preventable LBW: Cigarette smoking accounts for 9.6%; alcohol consumption during pregnancy, 2.3%; low pre-pregnancy weight (less than 54 kg), 6.3%; urinary tract infections, 1.3%; Chlamydia trachomatis genital infections, 4.8%; and narcotics addiction, 3.8%. Because these risk factors are not mutually exclusive, eg, narcotics addicts may be addicted to both narcotics and cigarettes, the maximum preventable population-attributable risk percentage for LBW is less than the sum of the individual risk factors, which is 28.1% (9.6% [cigarette smoking] + 2.3% [alcohol consumption] + 6.3% [low pre-pregnancy weight] + 1.3% [urinary tract infection] + 4.8% [Chlamydia] + 3.8% [narcotics addiction] = 28.1%). Given the current state of knowledge about preventable risk factors, LBW can be reduced--in an idealized model--from only 6.9 to 5.0% of all births. In a more realistic model, we estimate that LBW can be reduced from only 6.9 to 6.3% of all births. Therefore, a national effort is indicated to identify unknown preventable causes of LBW.

Pregnancy outcome after expectant management of premature rupture of the membranes in the second trimester.

Because management of premature rupture of the membranes (PROM) at or before 26 weeks is controversial, we examined maternal and perinatal outcome after expectant management of 44 pregnancies complicated by this problem. Mean gestational age at preterm PROM was 23.9 +/- 1.7 (SD) weeks. The latency period between preterm PROM and delivery ranged from 1 to 68 days, with a medium of 6. Of the patients, 54.6% delivered within a week of PROM, and 79.5% delivered by four weeks; 77.2% developed chorioamnionitis, but despite this high incidence, there was no maternal sepsis or pelvic thrombophlebitis, and no maternal surgery was necessary. Perinatal outcome was 60.5% neonatal survival, 54.2% perinatal survival and a stillbirth rate of 10.4%. Respiratory distress syndrome, bronchopulmonary dysplasia, sepsis and intraventricular hemorrhage were common types of neonatal morbidity. There was no pulmonary hypoplasia, and limb deformity was seen in only two neonates. Costs of expectant management in pregnancies complicated by second-trimester PROM were estimated, and a strategy to reduce cost is suggested.

Significance of positive cervical cultures for Chlamydia trachomatis in patients with preterm premature rupture of membranes.

We tested the hypothesis that in patients with preterm premature rupture of membranes the presence of Chlamydia trachomatis in the cervix shortens the latent period (time from rupture of membranes to delivery) and increases the incidence of chorioamnionitis and early endometritis. A total of 178 conservatively managed patients with PROM between 22 and 35 weeks' gestation had cervical cultures for chlamydia, group B Streptococcus (GBS) and Neisseria gonorrhoeae performed at the time of rupture. Patients with GBS and gonorrhea were treated at the time the culture results were available and excluded from analysis. The remaining patients were divided into group 1: 26 patients (14.6%) positive for only chlamydia (and not treated until discharge from the hospital); group 2: 120 patients (67.4%) negative for all three organisms. The two groups did not differ in cesarean rate, duration of conservative management, hospital stay, or birthweight. Furthermore, the rates of chorioamnionitis (30.8% group 1; 38.3% group 2) or early endometritis (11.5% group 1; 20.8% group 2) were similar. We conclude that in patients with preterm premature rupture of membranes, the presence of chlamydia in the cervix appears to neither decrease the latent period nor increase the incidence of chorioamnionitis and early endometritis.

Umbilical cord blood gases and mortality and morbidity in the very low birth weight infant.

Umbilical cord blood gas values and morbidity and mortality were correlated in 191 very low birth weight (VLBW) infants (500-1500 g). The mean umbilical arterial pH and base excess differed significantly between survivors and non-survivors. The presence of at least moderate acidosis (arterial pH 7.15 or lower) was related significantly to mortality, particularly in infants younger than 26 weeks. The mean cord blood gas values did not predict the presence or severity of hyaline membrane disease or intraventricular hemorrhage, but Apgar scores did. Bronchopulmonary dysplasia, neurologic sequelae, necrotizing enterocolitis, and sepsis also did not correlate with mean cord gas values, but neither did Apgar scores. Furthermore, the severity and type of acidosis did not relate to morbidity. Combining cord blood gases and Apgar scores did not help predict morbidity, which was not surprising because cord pH values correlated poorly with Apgar scores (all r values less than or equal to 0.26). We urge caution in interpreting cord gases as predictors of morbidity in the VLBW infant.

Cesarean: changing the trends.

A rising cesarean birth rate, both nationally and at our institution, led us to attempt to reverse the trend. Vaginal birth after cesarean (VBAC) was introduced as an alternative to repeat cesarean in 1982. The impact of VBAC on the cesarean rate for our institution was assessed from 1982-1988. Over the period studied, the rate of repeat cesarean rose from 5.0% in 1982 to 6.9% in 1985, then steadily fell to 5.3% in 1988. During this same period, the primary cesarean rate rose from 7.5% in 1982 to 11.9% in 1986, then declined to 10.6% in 1988. Changes in the rate for all cesareans paralleled those for primary procedures: 12.5% in 1982, 17.6% in 1986, and 15.9% in 1988. In patients with a history of previous cesarean, the relative risk of repeat cesarean dropped from 10.2 (95% confidence interval 8.8-11.8) in 1982 to 5.2 (95% confidence interval 4.5-6.0) in 1988. In the face of a rising rate of primary cesarean births, the introduction of VBAC has helped to stabilize the overall cesarean rate at our institution.