Steven L. Bloom

Birth Weight in Relation to Morbidity and Mortality among Newborn Infants

BACKGROUND At any given gestational age, infants with low birth weight have relatively high morbidity and mortality. It is not known, however, whether there is a threshold weight below which morbidity and mortality are significantly greater, or whether that threshold varies with gestational age. METHODS We analyzed the neonatal outcomes of death, five-minute Apgar score, umbilical-artery blood pH, and morbidity due to prematurity for all singleton infants delivered at Parkland Hospital, Dallas, between January 1, 1988, and August 31, 1996. A distribution of birth weights according to week of gestation at birth was created. Infants in the 26th through 75th percentiles for weight served as the reference group. Data on preterm infants (those born at 24 to 36 weeks of gestation) were analyzed separately from data on infants delivered at term (37 or more weeks of gestation). RESULTS A total of 122,754 women and adolescents delivered singleton live infants without malformations between 24 and 43 weeks of gestation. Among the 12,317 preterm infants who were analyzed, there was no specific birth-weight percentile at which morbidity and mortality increased. Among 82,361 infants who were born at term and whose birth weights were at or below the 75th percentile, however, the rate of neonatal death increased from 0.03 percent in the reference group (26th through 75th percentile for weight) to 0.3 percent for those with birth weights at or below the 3rd percentile (P<0.001). The incidence of five-minute Apgar scores of 3 or less and umbilical-artery blood pH values of 7.0 or less was approximately doubled for infants at or below the 3rd birth-weight percentile (P=0.003 and P<0.001, respectively). The incidence of intubation at birth, seizures during the first day of life, and sepsis was also significantly increased among term infants with birth weights at or below the 3rd percentile. These differences persisted after adjustment for the mothers race and parity and the infants sex. CONCLUSIONS Mortality and morbidity are increased among infants born at term whose birth weights are at or below the 3rd percentile for their gestational age.

Risk of uterine rupture with a trial of labor in women with multiple and single prior cesarean delivery

OBJECTIVE: To determine whether the risk for uterine rupture is increased in women attempting vaginal birth after multiple cesarean deliveries. METHODS: We conducted a prospective multicenter observational study of women with prior cesarean delivery undergoing trial of labor and elective repeat operation. Maternal and perinatal outcomes were compared among women attempting vaginal birth after multiple cesarean deliveries and those with a single prior cesarean delivery. We also compared outcomes for women with multiple prior cesarean deliveries undergoing trial of labor with those electing repeat cesarean delivery. RESULTS: Uterine rupture occurred in 9 of 975 (0.9%) women with multiple prior cesarean compared with 115 of 16,915 (0.7%) women with a single prior operation (P = .37). Multivariable analysis confirmed that multiple prior cesarean delivery was not associated with an increased risk for uterine rupture. The rates of hysterectomy (0.6% versus 0.2%, P = .023) and transfusion (3.2% versus 1.6%, P < .001) were increased in women with multiple prior cesarean deliveries compared with women with a single prior cesarean delivery attempting trial of labor. Similarly, a composite of maternal morbidity was increased in women with multiple prior cesarean deliveries undergoing trial of labor compared with those having elective repeat cesarean delivery (odds ratio 1.41, 95% confidence interval 1.02–1.93). CONCLUSION: A history of multiple cesarean deliveries is not associated with an increased rate of uterine rupture in women attempting vaginal birth compared with those with a single prior operation. Maternal morbidity is increased with trial of labor after multiple cesarean deliveries, compared with elective repeat cesarean delivery, but the absolute risk for complications is small. Vaginal birth after multiple cesarean deliveries should remain an option for eligible women. LEVEL OF EVIDENCE: II-2

Cesarean delivery: a randomized trial of epidural analgesia versus intravenous meperidine analgesia during labor in nulliparous women.

Background Controversy concerning increased cesarean births as a result of epidural analgesia for relief of labor pain has been attributed, in large part, to difficulties interpreting published studies because of design flaws. In this study, the authors compared epidural analgesia to intravenous meperidine analgesia using patient-controlled devices during labor to evaluate the effects of labor epidural analgesia, primarily on the rate of cesarean deliveries while minimizing limitations attributable to study design. Methods Four hundred fifty-nine nulliparous women in spontaneous labor at term were randomly assigned to receive either epidural analgesia or intravenous meperidine analgesia. Epidural analgesia was initiated with 0.25% bupivacaine and was maintained with 0.0625% bupivacaine and fentanyl 2 &mgr;g/ml at 6 ml/h with 5-ml bolus doses every 15 min as needed using a patient-controlled pump. Women in the intravenous analgesia group received 50 mg meperidine with 25 mg promethazine hydrochloride as an initial bolus, followed by 15 mg meperidine every 10 min as needed, using a patient-controlled pump. A written procedural manual that prescribed the intrapartum obstetric management was followed for each woman randomized in the study. Results A total of 226 women were randomized to receive epidural analgesia, and 233 women were randomized to receive intravenous meperidine analgesia. Protocol violations occurred in 8% (38 of 459) of women. There was no difference in the rate of cesarean deliveries between the two analgesia groups (epidural analgesia, 7% [16 of 226; 95% confidence interval, 4–11%]vs. intravenous meperidine analgesia, 9% [20 of 233; 95% confidence interval, 5–13%];P = 0.61). Significantly more women randomized to epidural analgesia had forceps deliveries compared with those randomized to meperidine analgesia (12% [26 of 226]vs. 3% [7 of 233];P < 0.001). Women who received epidural analgesia reported lower pain scores during labor and delivery compared with women who received intravenous meperidine analgesia. Conclusions Epidural analgesia compared with intravenous meperidine analgesia during labor does not increase cesarean deliveries in nulliparous women.

A prospective observational study of domestic violence during pregnancy.

Objective: To assess whether women reporting domestic violence are at increased risk for adverse pregnancy outcomes. Methods: A screening questionnaire, previously validated for the identification of female victims of domestic violence, was offered to women presenting to our Labor and Delivery Unit. The survey prompted women to indicate whether her partner or family member physically hurt her, insulted or talked down to her, threatened her with harm, or screamed or cursed at her. The primary study outcome was to detect a 3-fold increase in low birth weight infants (≤ 2,500 g) in women reporting physical abuse, compared with those not reporting domestic violence. Results: A total of 16,041 women were approached to be interviewed. Of these, 949 (6%) women responded affirmatively to one or more of the survey questions, and another 94 (0.6%) declined to be interviewed. The incidence of low birth weight infants was significantly increased in women who reported verbal abuse, compared with the no-abuse group (7.6% versus 5.1%, respectively, P = .002). Physical abuse was associated with an increased risk of neonatal death (1.5% versus 0.2%, P = .004). Interestingly, women who declined to be interviewed had significantly increased rates of low birth weight infants (12.8% versus 5.1%, P < .001), preterm birth at 32 weeks of gestation or less (5.3% versus 1.2%, P = .002), placental abruptions (2.1% versus 0.2%, P < .001), and neonatal intensive care admissions (7.4% versus 2.2%, P = .008) when compared with women in the no-abuse group, respectively. Conclusion: Women who declined to be surveyed regarding domestic violence were at increased risk for adverse pregnancy outcome. Level of Evidence: II-2

Decision-to-incision times and maternal and infant outcomes.

OBJECTIVE: To measure decision-to-incision intervals and related maternal and neonatal outcomes in a cohort of women undergoing emergency cesarean deliveries at multiple university-based hospitals comprising the National Institute of Child Health and Human Development Maternal–Fetal Medicine Units Network. METHODS: All women undergoing a primary cesarean delivery at a Network center during a 2-year time span were prospectively ascertained. Emergency procedures were defined as those performed for umbilical cord prolapse, placental abruption, placenta previa with hemorrhage, nonreassuring fetal heart rate pattern, or uterine rupture. Detailed information regarding maternal and neonatal outcomes, including the interval from the decision time to perform cesarean delivery to the actual skin incision, was collected. RESULTS: Of the 11,481 primary cesarean deliveries, 2,808 were performed for an emergency indication. Of these, 1,814 (65%) began within 30 minutes of the decision to operate. Maternal complication rates, including endometritis, wound infection, and operative injury, were not related to the decision-to-incision interval. Measures of newborn compromise including umbilical artery pH less than 7 and intubation in the delivery room were significantly greater when the cesarean delivery was commenced within 30 minutes, likely attesting to the need for expedited delivery. Of the infants with indications for an emergency cesarean delivery who were delivered more than 30 minutes after the decision to operate, 95% did not experience a measure of newborn compromise. CONCLUSION: Approximately one third of primary cesarean deliveries performed for emergency indications are commenced more than 30 minutes after the decision to operate, and the majority were for nonreassuring heart rate tracings. In these cases, adverse neonatal outcomes were not increased. LEVEL OF EVIDENCE: II-2

Second-stage labor duration in nulliparous women: relationship to maternal and perinatal outcomes

OBJECTIVE The purpose of this study was to assess maternal and perinatal outcomes as a function of second-stage labor duration. STUDY DESIGN We assessed outcomes in nulliparous laboring women who were enrolled in a trial of fetal pulse oximetry. RESULTS Of 5341 participants, 4126 women reached the second stage of labor. As the duration of the second stage increased, spontaneous vaginal delivery rates declined, from 85% when the duration was <1 hour to 9% when it was > or =5 hours. Adverse maternal outcomes that were associated significantly with the duration of the second stage of labor included chorioamnionitis (overall rate, 3.9%), third- or fourth-degree perineal laceration (overall rate, 8.7%), and uterine atony (overall rate, 3.9%). Odds ratios for each additional hour of the second stage of labor ranged from 1.3-1.8. Among individual adverse neonatal outcomes, only admission to a neonatal intensive care unit was associated significantly with second stage duration (odds ratio, 1.4). CONCLUSION The second stage of labor does not need to be terminated for duration alone.

Pitfalls in ultrasonic cervical length measurement for predicting preterm birth.

OBJECTIVE To describe the anatomic and technical difficulties encountered with transvaginal ultrasound imaging of the cervix in a consecutive series of women at risk for preterm delivery. METHODS Three groups of women had cervical ultrasound examinations: those with histories of preterm birth, those with incompetent cervices, and those admitted for preterm labor that did not progress. Standardized ultrasound examinations of the cervix involved measuring the length of the endocervical canal, funneling length, and internal os dilation with and without fundal pressure. RESULTS Sixty consecutive women had transvaginal ultrasound examinations for assessment of the cervix. Forty-six had histories of preterm birth, five had incompetent cervices, and nine had arrested preterm labor. Six types of problems arose, which can be divided into anatomic or technical considerations, with an overall frequency of 27% (95% confidence interval 16%, 40%). Anatomic pitfalls that hampered identification of the internal os included an undeveloped lower uterine segment (n = 5), a focal myometrial contraction (n = 1), rapid and spontaneous cervical change (n = 1), and an endocervical polyp (n = 1). Technical pitfalls included incorrect interpretation of internal os dilation because of vaginal probe orientation (n = 7) and artificial lengthening of the endocervical canal because of distortion of the cervix by the transducer (n = 1). CONCLUSION We caution those who perform cervical length examinations to be wary of falsely reassuring findings due to potential anatomic and technical pitfalls.

Ampicillin for neonatal group B streptococcal prophylaxis: How rapidly can bactericidal concentrations be achieved?

OBJECTIVE Our purpose was to determine how rapidly bactericidal concentrations of ampicillin against group B streptococci are achieved in amniotic fluid and cord blood after a 2 gm maternal infusion. STUDY DESIGN Ampicillin was administered at varying time intervals between 3 and 67 minutes before elective cesarean delivery in 40 women. Samples of amniotic fluid were obtained by amniocentesis just before the uterine incision was made. Umbilical and maternal blood were obtained at the time of delivery. Ampicillin concentrations were measured by high-pressure liquid chromatography. RESULTS The mean concentrations of ampicillin measured in maternal and umbilical cord sera all exceeded the minimum bactericidal concentrations reported for group B streptococci (0.25 to 2.0 micrograms/ml) and were achieved as soon as 5 minutes after ampicillin infusion. Similarly, bactericidal levels of ampicillin in the amniotic fluid could be detected as early as 5 minutes. However, such concentrations of ampicillin in the amniotic fluid were achieved in only 85% of the pregnancies studied. CONCLUSIONS Bactericidal levels of ampicillin against group B streptococci can usually be achieved rapidly in both fetal blood and amniotic fluid after a standard 2 gm intravenous dose given to the mother for neonatal prophylaxis.

Severe preeclampsia and the very low birth weight infant: is induction of labor harmful?

OBJECTIVE To compare the effects of labor induction with the effects of cesarean delivery without labor on neonatal outcome in pregnancies complicated by severe preeclampsia and delivery of very low birth weight infants. METHODS This was a retrospective study of 278 singleton, live-born infants who weighed 750-1500 g and were delivered because of severe preeclampsia between 1988 and 1997. Outcomes of infants delivered by cesarean without labor were compared with those of infants exposed to labor induction. Statistical analysis was performed using Student t test, Mann-Whitney U test, chi2 analysis, and Fisher exact test, where appropriate. Multiple logistic regression analysis was used to adjust for outcomes of interest. RESULTS One hundred forty-five (52%) of the 278 women with severe preeclampsia who delivered infants weighing between 750 and 1500 g had labor induced and 133 (48%) delivered by cesarean without labor. Vaginal delivery was accomplished by 50 (34%) women in the induced group. Apgar scores of 3 or less at 5 minutes were more likely in the induced-labor group (6 versus 2%, P = .04), but other neonatal outcomes, including respiratory distress syndrome, grade 3 or 4 intraventricular hemorrhage, sepsis, seizures, and neonatal death, were similar in the two groups. Adjustment for birth weight and gestational age did not affect those results. Analysis of data from the induced-labor group did not reveal an effect by route of delivery on neonatal outcome. CONCLUSION Induction of labor in cases of severe preeclampsia is not harmful to very low birth weight infants.

Failed Labor Induction Toward an Objective Diagnosis

OBJECTIVE: To evaluate maternal and perinatal outcomes in women undergoing labor induction with an unfavorable cervix according to duration of oxytocin administration in the latent phase of labor after ruptured membranes. METHODS: This was a secondary analysis of a randomized multicenter trial in which all cervical examinations from admission were recorded. Inclusion criteria: nulliparas at or beyond 36 weeks of gestation undergoing induction with a cervix of 2 cm or less dilated and less than completely effaced. The latent phase of labor was defined as ending at a cervical dilation of 4 cm and effacement of at least 90%, or at a cervical dilation of 5 cm regardless of effacement. RESULTS: A total of 1,347 women were analyzed. The overall vaginal delivery rate was 63.2%. Most women had exited the latent phase after 6 hours of oxytocin and membrane rupture (n=939; 69.7%); only 5% remained in the latent phase after 12 hours. The longer the latent phase, the lower the vaginal delivery rate. Even so, 39.4% of the 71 women who remained in the latent phase after 12 hours of oxytocin and membrane rupture were delivered vaginally. Chorioamnionitis, endometritis, or both, and uterine atony were the only maternal adverse outcomes related to latent-phase duration: adjusted odds ratios (95% confidence intervals) of 1.12 (1.07, 1.17) and 1.13 (1.06, 1.19), respectively, for each additional hour. Neonatal outcomes were not related to latent-phase duration. CONCLUSION: Almost 40% of the women who remained in the latent phase after 12 hours of oxytocin and membrane rupture were delivered vaginally. Therefore, it is reasonable to avoid deeming labor induction a failure in the latent phase until oxytocin has been administered for at least 12 hours after membrane rupture. LEVEL OF EVIDENCE: III