Vaginal birth after cesarean: an appraisal of fetal risk.

OBJECTIVE: To expand on prior investigations and further evaluate the fetal risk associated with vaginal birth after cesarean (VBAC) by examining the incidence not only of a depressed Apgar score at 5 minutes but also of fetal acidemia. METHODS: Between January 1, 1991, and December 31, 1996, the following groups of patients who delivered a singleton fetus with birth weight greater than 750 g were identified: 2082 patients with one or more prior cesarean deliveries who were allowed a trial of labor, 1677 of whom delivered vaginally and 405 of whom delivered by repeat cesarean; 920 patients delivered by elective repeat cesarean; 22,863 patients without a prior cesarean who delivered vaginally; and 2432 patients delivered by primary cesarean after laboring. Umbilical cord arterial blood gases were obtained in 88.3% of these deliveries. Comparisons of Apgar scores at 5 minutes and umbilical cord arterial pH measurements were made between groups with chi2 or Fisher exact test, and odds ratios (ORs) were calculated. RESULTS: The only significant differences were noted between those patients who delivered vaginally after a prior cesarean and those patients who delivered vaginally without a prior cesarean. Neonates in the successful VBAC group were more likely to have an Apgar score at 5 minutes less than 7 (OR 1.52) or an umbilical arterial pH less than 7.1 (OR 1.69). Those neonates, however, were not at greater risk for an Apgar score less than 4 or a pH less than 7.0. CONCLUSION: Our experience suggests that VBAC poses a low level of fetal risk, although a much larger sample size would be required to exclude a two-fold increase in potentially damaging fetal acidemia.

Ultrasonic fetal weight prediction: role of head circumference and femur length.

The accurate sonographic estimate of fetal weight is helpful in those instances when the fetal weight estimate might alter clinical management. Most sonographic weight predicting formulas have been based predominantly on measurements from the term fetus and then applied to the preterm fetus. Yet, the morphology of the preterm and term fetus differs considerably. The authors have examined the predictive accuracy of three published sonographic formulas in 69 preterm fetuses scanned within 48 hours of delivery. The mean birth weight was 1396 g. Thirty-nine of the infants were less than 1500 g. Sixty-two percent were products of pregnancies complicated by premature rupture of membranes. The results were compared with new equations derived from combinations of head and abdominal circumferences, biparietal diameter, and femur length obtained from the first 33 fetuses and then tested on the remaining 36. Whereas each formula correlated highly with birth weight, the selected new formula was more accurate than the published formulas by each criteria examined. In contrast to the latter, the mean error (actual minus predicted weight) of most new equations did not significantly differ from zero when tested prospectively. In addition, it appeared that the accuracy of two new formulas not incorporating femur length could be further enhanced in the group of fetuses whose femur length differed from the mean by at least 2 standard deviations by multiplying the predicted weight by the ratio of actual to mean femur length. The authors conclude that the use of head circumference and femur length coupled with a population restricted to the preterm fetus enhances the accuracy of sonographic weight predictions.

Cost-effectiveness of elective cesarean delivery after one prior low transverse cesarean.

OBJECTIVE: This analysis was undertaken to better understand the costs and health consequences of a trial of labor after cesarean when compared with a policy of routine elective repeat cesarean delivery. METHODS: A decision-tree model incorporating a Markov analysis was used to examine the reproductive life of a hypothetical cohort of 100,000 pregnant women whose only prior pregnancy was delivered through a low transverse cesarean incision. Using this model, the policy of performing routine elective cesarean delivery was compared with a policy of allowing a trial of labor. Main outcome measures were maternal and neonatal morbidity and mortality, total costs to the health care system, and cost per major neonatal complication avoided (death or permanent neurologic sequelae). RESULTS: The consequences of routine elective cesarean delivery for a second birth are significant, with an additional 117,748 cesarean deliveries, 5500 maternal morbid events, and $179 million incurred during the reproductive life of 100,000 women. The prevention of one major adverse neonatal outcome requires 1591 cesarean deliveries and $2.4 million. Sensitivity analysis confirms the robustness of the analysis. CONCLUSION: Routine elective cesarean for a second delivery for women with a prior low transverse cesarean incision results in an excess of maternal morbidity and mortality and a high cost to the medical system.

Diminished biparietal diameter and abdominal circumference growth in twins.

Forty-three women with uncomplicated twin pregnancies and reliable menstrual dates had serial ultrasonic measurements of the fetal biparietal diameter (BPD) and abdominal circumference. The 25th, 50th, and 75th fetal BPD and abdominal circumference growth percentiles were generated from this normal twin population and compared with those for singletons. A slowing of both BPD and abdominal circumference growth in twins was noted in the third trimester. However, newborn anthropometric data were collected that suggest that the head circumference of twins is comparable to that of singletons. This discrepancy between ultrasonic BPD and neonatal head circumference in predicting head size may possibly be explained by dolichocephaly attributed to uterine crowding. For the antenatal assessment of growth in twins the authors recommend the use of BPD and abdominal circumference charts derived specifically from such uncomplicated twin pregnancies. When the BPD growth is abnormal, the head circumference and abdominal circumference should be measured to assess whether or not fetal growth is normal.

Urinary estriols in diabetic pregnancy: a reappraisal.

The clinical usefulness of serial urinary estriols was tested in 138 insulin-dependent diabetic pregnant women. No action was taken on an estriol drop if fetal well-being was demonstrated by a reactive nonstress test and/or negative contraction stress test within 24 hours. Of 3085 estriol values, a greater than or equal to 40% estriol drop, confirmed by a greater than or equal to 40% decrease in the estriol-creatine ratio, was observed in 21 tests. In only two of these tests, was fetal distress indicated by a nonstress test or contraction stress test. A significant linear correlation was demonstrated between the mean level of estriol excretion and birth weight, placental weight, and fetal abdominal circumference measured by ultrasound. Chronically low estriol excretion (less than 12 mg per 24 hours at greater than 36 weeks' gestation) related to smaller placentas but not to fetal jeopardy.

Placenta accreta is associated with elevated maternal serum alpha-fetoprotein.

OBJECTIVE: To determine whether placenta accreta/percreta/increta is associated with elevation of second-trimester maternal serum alpha-fetoprotein (MSAFP) levels. METHODS: We reviewed the medical records of 44 women who had emergency cesarean hysterectomy. Twenty women had placenta accreta/percreta/increta (study group) and 24 underwent cesarean hysterectomy for other indications (control group). Pertinent maternal and neonatal variables were abstracted from the prenatal records and hospital charts. Chi-square and Fisher exact tests were used to analyze categorical variables. Student t test was used to analyze continuous variables. RESULTS: Nine of 20 patients (45%) with placenta accreta/percreta/increta and none of 24 subjects in the control group had an elevated MSAFP value (P < .001). Maternal estimated blood loss was also significantly greater in the study group (4469 +/- 1851 versus 1885 +/- 1113 mL; P < .0001), as was the number of blood units transfused (7.7 +/- 4.7 versus 3.0 +/- 2.2; P < .001). None of the other examined variables were different between the groups. CONCLUSIONS: A significant association exists between placenta accreta/percreta/increta and elevated MSAFP values. Patients with an unexplained elevation of MSAFP may have an increased risk for placenta accreta and associated blood loss at cesarean hysterectomy.

Soluble tumor necrosis factor receptors and interleukin-6 levels in patients with severe preeclampsia.

OBJECTIVE: To investigate whether serum and amniotic fluid (AF) levels of soluble tumor necrosis factor receptors and interleukin-6, markers of immune activation and endothelial dysfunction, are altered in patients with severe preeclampsia. METHODS: Plasma was collected before induction of labor, at delivery, and postpartum from 19 patients with severe preeclampsia. Amniotic fluid was also obtained in early labor from these patients. Similar samples were obtained from an antepartum control group matched for gestational age and a term control group without preeclampsia. All plasma and AF samples were assayed for p55 and p75 soluble tumor necrosis factor receptors and for interleukin-6 by specific enzyme-linked immunoassays. Levels in preeclamptic patients and the control groups were compared. RESULTS: Levels of both receptors were significantly elevated in AF and all maternal plasma samples except those collected 24 hours postpartum for patients with preeclampsia relative to levels in controls. Interleukin-6 was detected more frequently and in higher concentrations in the plasma collected before labor for preeclamptic patients compared with controls, but no difference was noted in interleukin-6 detection rates or plasma concentrations at delivery. Conversely, AF concentrations of interleukin-6 were significantly reduced in patients with preeclampsia. CONCLUSION: The increased levels of soluble tumor necrosis factor receptors found in patients with severe preeclampsia may represent a protective response to increased tumor necrosis factor activity and be a marker for immune activation. Increased interleukin-6 concentrations in maternal plasma before labor suggest the involvement of this cytokine as well in the altered immune response and its contribution to endothelial cell dysfunction.

Diabetic macrosomia: accuracy of third trimester ultrasound.

Sonar biparietal diameter, head circumference, and abdominal circumference percentile values obtained late in the third trimester were compared with birth weight percentile (relative to dates) in 147 diabetic mothers and 40 control fetuses of nondiabetics. Estimates of fetal weight by the method of Shepard et al were also calculated from these sonar data and compared with birth weight percentile. Abdominal circumference values greater than the 90th percentile correctly predicted macrosomia (defined as birth weight greater than 90th percentile) in 78% of cases. Biparietal diameter and head circumference percentiles were significantly less predictive of macrosomia. When analyzed in a similar manner, estimated fetal weights greater than the 90th percentile correctly predicted macrosomia at birth in 74% of cases. However, when both the abdominal circumference and the estimated fetal weight exceeded the 90th percentile, macrosomia was correctly diagnosed in 88.8% of pregnant women with diabetes mellitus.

Risk of cesarean delivery with elective induction of labor at term in nulliparous women.

OBJECTIVE: To quantify the risk of cesarean delivery associated with elective induction of labor in nulliparous women at term. METHODS: We performed a cohort study on a major urban obstetric service that serves predominantly private obstetric practices. All term, nulliparous women with vertex, singleton gestations who labored during an 8-month period (n = 1561) were divided into three groups: spontaneous labor, elective induction, and medical induction. The risk of cesarean delivery in the induction groups was determined using stepwise logistic regression to control for potential confounding factors. RESULTS: Women experiencing spontaneous labor had a 7.8% cesarean delivery rate, whereas women undergoing elective labor induction had a 17.5% cesarean delivery rate (adjusted odds ratio [OR] 1.89; 95% confidence interval [CI] 1.12, 3.18) and women undergoing medically indicated labor induction had a 17.7% cesarean delivery rate (OR 1.69; 95% CI 1.13, 2.54). Other variables that remained significant risk factors for cesarean delivery in the model included: epidural placement at less than 4 cm dilatation (OR 4.66; 95% CI 2.25, 9.66), epidural placement after 4 cm dilatation (OR 2.18; 95% CI 1.06, 4.48), chorioamnionitis (OR 4.61; 95% CI 2.89, 7.35), birth weight greater than 4000 g (OR 2.59; 95% CI 1.69, 3.97), maternal body mass index greater than 26 kg/m2 (OR 2.36; 95% CI 1.61, 3.47), Asian race (OR 2.35; 95% CI 1.04, 5.34), and magnesium sulfate use (OR 2.18; 95% CI 1.04, 4.55). CONCLUSION: Elective induction of labor is associated with a significantly increased risk of cesarean delivery in nulliparous women. Avoiding labor induction in settings of unproved benefit may aid efforts to reduce the primary cesarean delivery rate.

Iatrogenic respiratory distress syndrome following elective repeat cesarean delivery.

OBJECTIVE: To determine the incidence of iatrogenic respiratory distress syndrome (RDS) following elective repeat cesarean delivery and to identify whether it was associated with departures from accepted management guidelines. METHODS: Between January 1986 and March 1991, there were 23,125 deliveries at Northwestern Memorial Hospital, of which 1207 were repeat cesarean births without labor. During this period, 18 neonates of 37 weeks' gestation or greater or 2500 g or greater who were delivered by elective repeat cesarean were admitted to the neonatal intensive care unit (NICU) for respiratory difficulties. RESULTS: Five of the 18 neonates admitted to the NICU with respiratory difficulty following elective repeat cesarean delivery met the criteria for RDS. This represents an incidence of 0.41% (five of 1207), or one case of RDS for every 241 repeat cesarean deliveries without labor. Four of the five neonates required mechanical ventilation for an average of 6.8 days. The average NICU stay was 11.2 days. Complications included pneumothorax (one) and pulmonary hemorrhage (one). Departures from accepted management guidelines included a discrepancy between ultrasound and menstrual dates (two), no confirmation of menstrual dates (one), and delivery before 39 weeks' gestation (two). CONCLUSION: Iatrogenic RDS continues to occur in the setting of elective repeat cesarean delivery and is associated with a failure to adhere to clinical protocols.

Diagnosis of fetal death in utero by real-time ultrasound.

The efficacy of real-time ultrasound for the diagnosis of fetal death or hydatidiform mole was evaluated during a 1-year period. During this time, 116 patients were referred to the obstetric ultrasound service for the confirmation of clinical diagnoses. In 24 of 46 patients (52%) presenting in the first half of pregnancy, the referring diagnosis was confirmed. In 1 case of an early intrauterine pregnancy with a degenerating myoma, the ultrasound diagnosis of molar pregnancy was in error. In 48 of 70 patients (69%) referred after 20 weeks' gestation, the clinical diagnosis was confirmed. In no instance was either a false-positive or false-negative diagnosis made with real-time ultrasound in the last half of pregnancy. This method should prove to be the method of choice in diagnosing intrauterine fetal death.

Active management of labor.

The active management of labor may be one approach to achieving lower rates of intervention. Numerous institutions have reported lower CS rates since initiating this labor management scheme, and concurrent decreases in the length of labor and infectious morbidity have been demonstrated. Sufficient data now exist to conclude that such programs can be instituted without deleterious effects on neonatal outcomes. Nevertheless, success in decreasing CS rates has not been uniform and may be confined to certain settings. Other approaches to labor management may be as good or better at achieving low rates of intervention with minimum morbidity. Any approach that emphasizes advocacy for vaginal birth is likely to produce some success and should receive support.

Apgar scores and umbilical cord arterial pH in the breech neonate.

Apgar scores and umbilical cord arterial pH measurements of 449 singleton breech deliveries are compared retrospectively to those of 1425 singleton vertex neonates. In the vaginal deliveries the Apgar scores and umbilical arterial pH were higher for the vertex neonates. There were no differences in either Apgar scores or umbilical arterial pH between the breech and vertex neonates delivered by cesarean section. Whereas Apgar scores in the less than 1000 g and greater than or equal to 2500 g weight groups were lower in the breech neonates delivered vaginally compared to cesarean section, umbilical arterial pH measurements were similar. The data suggest that liberal use of cesarean section may improve the Apgar scores but will probably not appreciably improve the acid-base status of the breech neonate.

Perinatal outcome following intravascular transfusion in severely isoimmunized fetuses.

Twenty-six severely isoimmunized pregnancies managed exclusively with ultrasonographically guided intravascular fetal transfusions are reported. The mean gestational age plus and minus one standard deviation (+/- SD) was 26.3 +/- 3.6 weeks and the mean hematocrit (+/- SD) prior to initial transfusion was 20.6 +/- 6.7%. Four of seven hydropic fetuses and 9 of 19 without hydrops were less than or equal to 26 weeks gestation at the first transfusion. Overall survival was 85% (22/26). Survival was similar whether or not fetal hydrops was present (6/7 vs. 16/19) and whether or not the first transfusion was administered at less than or equal to 26 weeks gestation (10/13 vs. 12/13).

The tap test: confirmation of a simple, rapid, inexpensive, and reliable indicator of fetal pulmonary maturity.

The tap test was previously described, and preliminary experience suggested it might be a rapid, inexpensive, and reliable indicator of fetal lung maturity. In this expanded series of 332 patients delivered of infants within 72 hours of amniotic fluid analysis, the predictive values for mature test results at 2, 5, and 10 minutes were 98.9% (182 of 184), 97.4% (221 of 227), and 97.1% (233 of 240), respectively. Predictive values for immature test results were 41.2% (61 of 148), 54.3% (57 of 105), and 60.9% (56 of 92). For the phospholipid profile the predictive value was 96.9% (186 of 192) for a mature test result and 40.7% (57 of 140) for an immature result. These observations, coupled with its methodologic simplicity, make the tap test a good first step in a cascade scheme of tests for fetal lung maturity and a valuable test in a facility where the phospholipid profile is not available 24 hours a day.

Active management of labor.

Active management of labor was first instituted as a program to shorten the length of nulliparous labor. Numerous institutions have found that implementation of this program decreased rates of cesarean section. Two randomized trials have evaluated this program, with both showing that labor was shortened by approximately 2 hours and maternal infectious morbidity was decreased by approximately 50%. Although one trial demonstrated a significant reduction in the rate of cesarean birth, the other did not. No users have reported any increase in neonatal morbidity. For some institutions implementation of active management of labor principles may be one approach to decrease operative deliveries for dystocia.

Control of preeclamptic hypertension by ketanserin, a new serotonin receptor antagonist.

We investigated the effect of peripheral serotonin receptor blockade on preeclamptic hypertension in 20 postpartum patients by the use of ketanserin, a serotonin receptor antagonist. In a study consisting of a double-blind crossover with placebo, parenteral ketanserin significantly reduced blood pressure from 167/105 to 126/71 mm Hg compared to a decline from 157/98 to 150/91 mm Hg for the placebo (p less than 0.001). All patients became hypertensive again following infusion, although no abrupt rebound in pressure occurred. Side effects were minimal. The results demonstrate that preeclamptic hypertension can be controlled by ketanserin and suggest that serotonin may have a role in the modulation of preeclampsia.

The tap test: a rapid indicator of fetal pulmonary maturity.

We present here a new means to assess fetal pulmonary maturity called the tap test. It is rapid, inexpensive, and requires only 1 ml of amniotic fluid. The tap test was compared to the phospholipid profile in 88 fetuses, 70 of whom were delivered before term. All fetuses were born within 72 hours after the amniotic fluid specimen was obtained. The test results were correlated to the absence or presence of the neonatal respiratory distress syndrome. When the tap test was evaluated at 2, 5, and 10 minutes, the predictive values for a mature test result were 100%, 98%, and 98%; the predictive values for an immature test result were 43%, 52%, and 58%, respectively. For the phospholipid profile the predictive values for a mature and an immature test result were 98% and 37%. These findings indicate that the ability of the tap test to predict fetal pulmonary maturity is comparable, if not superior, to that of the phospholipid profile.

Depressed Apgar scores, acid-base status, and neurologic outcome.

OBJECTIVE: Our purpose was to determine the acid-base status of neonates with an Apgar score < or = 3 at 5 minutes and to ascertain whether accompanying acidemia is an important predictor of immediate newborn morbidity and long-term neurologic development. STUDY DESIGN: From January 1984 through December 1991 there were 28 newborns with gestational age > or = 34 weeks or birth weight > or = 2000 gm in whom the Apgar score at 5 minutes was < or = 3 and for whom umbilical cord arterial blood gas measurements were retrievable from the perinatal database. The neonates were grouped according to whether the immediate newborn course was complicated (n = 16) or uncomplicated (n = 12). Analysis of variables between these two groups and between those neonates in the complicated group who were later assessed to be developmentally normal (n = 6) or to have cerebral palsy (n = 6) was performed by Fisher's exact test, unpaired Student t test, Mann-Whitney U test, analysis of variance, or multiple logistic regression. RESULTS: Seventeen of 28 (60.7%) neonates with an Apgar score of < or = 3 at 5 minutes had an umbilical cord arterial pH > 7.00, and in 15 (53.6%) cases the pH was > 7.10. Neonates with a complicated newborn course had a significantly lower mean pH (6.94 +/- 0.19 vs 7.14 +/- 0.11, p < 0.01) and a significantly greater mean base deficit (14.8 +/- 6.3 mmol/L vs 6.4 +/- 4.0 mmol/L, p < 0.001). However, within this group there were no differences in umbilical cord arterial blood gas measurements between those children who were subsequently normal versus those with cerebral palsy. Multiple logistic regression analysis could not identify any newborn morbidity predictive of long-term neurologic development in those neonates with a complicated newborn course. CONCLUSIONS: Neonates with an Apgar score < or = 3 at 5 minutes and a complicated newborn course were more likely to be delivered by cesarean section for fetal heart rate abnormalities and to have lower umbilical cord arterial pH measurements and higher base deficit values than did their counterparts with an uncomplicated newborn course. No neonatal variable, however, was predictive of chronic neurologic disability within the group of neonates with a complicated newborn course.