Faculty Bibliography

OBJECTIVE: The study was undertaken to evaluate the influence of maternal race on fetal femur length when screening for Down syndrome. STUDY DESIGN: We reviewed our patient databases to obtain fetal biometry from 15 to 22 weeks' gestation, maternal race, and cases of Down syndrome. Institution and race-specific regression lines for femur length (FL) to biparietal diameter (BPD) were created. The efficiency of using published expected FL was compared with our institution and race-specific regression in screening for Down syndrome. RESULTS: There were 4350 African American, 4271 white, 2315 Hispanic, and 654 Asian subjects and 42 cases of Down syndrome (1:276) included in the study. Our institutionally derived regression for FL by BPD had an R(2) of 0.82. Regression lines for FL by BPD generated by race had an R(2) of 0.86, 0.84, 0.83, and 0.80 for African American, Hispanic, Asian, and white subjects, respectively. The race-specific regression was no better than institution-specific data. CONCLUSION: Using institution-specific FL was more efficient in screening for Down syndrome than published expected FL; race-specific analysis did not improve efficiency.

OBJECTIVE: To determine the influence of race and ethnicity on the expected humeral length based on biparietal diameter measured in second-trimester fetuses. METHODS: We searched our ultrasound, obstetric, and cytogenetic databases from 1995 through 2001 for all fetuses who underwent an anatomic survey between 15 and 22 weeks' gestation. Fetuses with Down syndrome were identified and removed for separate analysis. Linear regression curves were generated for humeral length by biparietal diameter according to race and ethnicity. Analysis of variance was used to compare the mean variation of observed from expected humeral length by biparietal diameter according to race and ethnicity. RESULTS: There were 11,278 humeral length-by-biparietal diameter pairs that were available for analysis in our population, including 4202 African American, 2269 Hispanic, 639 Asian, and 4168 white fetuses. Humeral length was highly correlated with biparietal diameter for each race (R2 = 0.8). There were no differences in mean variances according to race or ethnicity (P = .75). CONCLUSIONS: Race and ethnicity do not affect the mean regression line of expected humeral length by biparietal diameter among fetuses in the second trimester. Genetic sonographic norms, therefore, do not require race- or ethnic-specific formulas for humeral length.

OBJECTIVE: To evaluate the association of uterine rupture during a trial of labor after cesarean with postpartum fever after the prior cesarean delivery. METHODS: We conducted a nested, case-control study in a cohort of all women undergoing a trial of labor after cesarean over a 12-year period in a single tertiary care institution. The current study was limited to all women undergoing a trial of labor after cesarean at term with a symptomatic uterine rupture and who also had their prior cesarean at the same institution. Four controls, who all had their prior cesarean at the same institution, were matched to each case by year of delivery, number of prior cesareans, prior vaginal delivery, and induction in the index pregnancy. Medical records were reviewed for maximum postpartum temperature for the previous cesarean. Fever was defined as a temperature above 38C. Conditional logistic regression analysis was performed taking into account potential confounding factors. RESULTS: There were 21 cases of uterine rupture included in the analysis. The rate of fever following the prior cesarean was 38% (8/21) among the cases, and 15% (13/84) in the controls, P =.03. Multiple logistic regression analysis examining the association of uterine rupture and postpartum fever adjusting for confounders revealed an odds ratio of 4.0, 95% confidence interval 1.0, 15.5. CONCLUSION: Postpartum fever after cesarean delivery is associated with an increased risk of uterine rupture during a subsequent trial of labor.

OBJECTIVE: To estimate whether maternal age is associated with a symptomatic uterine rupture during a trial of labor after prior cesarean delivery. METHODS: We retrospectively reviewed the medical records of all patients undergoing a trial of labor after prior cesarean delivery over a 12-year period. We analyzed the labors of women with one prior cesarean and no prior vaginal deliveries. The uterine rupture rate was determined with respect to maternal age. Multiple logistic regression was used to control for potential confounding variables. RESULTS: Overall, 32 (1.1%) uterine ruptures occurred among 3015 women. For women younger than 30 years, the risk of uterine rupture was 0.5%, and for those women aged at least 30 years, the risk of uterine rupture was 1.4% (P =.02). Controlling for birth weight, induction, augmentation, and interdelivery interval, the odds ratio for symptomatic uterine rupture for women aged at least 30 years compared with those less than 30 years was 3.2 (95% confidence interval 1.2, 8.4). CONCLUSION: Women aged 30 years or older have a greater risk of uterine rupture as compared with women younger than 30 years.

OBJECTIVE: To investigate maternal perceptions of both pain and anxiety before and after genetic amniocentesis. STUDY DESIGN: This prospective study of midtrimester, singleton pregnancies was conducted between March 2000 and July 2000. Study variables included patient demographics, medical and obstetric histories, indication for amniocentesis and a description of the source of information used by the patient regarding the procedure and technical degree of difficulty. Maternal pain and anxiety associated with performing amniocentesis were subjectively quantified with the use of the visual analog scale (VAS). Statistical analysis included Wilcoxon signed rank test, anova, and simple and stepwise regression analyses. RESULTS: One hundred and eighty-three women participated in the study. Perception of pain before amniocentesis was significantly higher compared to that expressed immediately after the procedure, with a mean VAS score of 3.7 +/- 2.5 vs. 2.1 +/- 2.0 (P < 0.0001). Similarly, perception of anxiety was significantly greater prior to the procedure, with a mean VAS score of 4.6 +/- 2.8 vs. 2.8 +/- 2.4 after the amniocentesis (P < 0.0001). Perceptions of pain and anxiety were significantly and positively correlated to each other both before and after the procedure (P < 0.0001). History of a prior amniocentesis was the only variable associated with reducing expected pain and anxiety (negative correlation, P < 0.001), whereas the technical degree of difficulty was the only significant variable impacting on the actual pain and anxiety (positive correlation, P < 0.005). CONCLUSIONS: Preamniocentesis counseling should emphasize the fact that, for most women, the actual pain and anxiety experienced during the procedure are significantly lower than expected. In fact, on a scale of 0-10, the mean level of pain was only 2.1, with a slightly higher mean level of anxiety

OBJECTIVE: To compare outcomes at term of a trial of labor in women with previous cesarean delivery who delivered neonates weighing > 4000 g versus women with those weighing < or = 4000 g. STUDY DESIGN: We reviewed medical records for all women undergoing a trial of labor after prior cesarean delivery during a 12-year period. The current analysis was limited to women at term with one prior cesarean and no other deliveries. The rates of cesarean delivery and symptomatic uterine rupture for women with infants weighing > 4000 g were compared to the rates for women with infants weighing < or = 4000 g. Logistic regression was used to control for the potential confounding by use of epidural, maternal age, labor induction, labor augmentation, indication for previous cesarean, type of uterine hysterotomy, year of delivery, receiving public assistance, and maternal race. Adjusted odds ratios and 95% confidence intervals were calculated. RESULTS: Of 2749 women, 13% (365) had infants with birth weights > 4000 g. Cesarean delivery rate associated with birth weights < or = 4000 g was 29% versus 40% for those with birth weights > 4000 g (P = .001). With use of logistic regression, we found that birth weight > 4000 g was associated with a 1.7-fold increase in risk of cesarean delivery (95% CI, 1.3-2.2). The rate of uterine rupture for women with infants weighing < or = 4000 g was 1.0% versus a 1.6% rate for those with infants weighing > 4000 g (P = .24). Although the logistic regression analysis revealed a somewhat higher rate of uterine rupture associated with birth weights of > 4000 g (adjusted OR, 1.6; 95% CI, 0.7-4.1), this difference was not statistically significant. The rate of uterine rupture was 2.4% for women with infants weighing > 4250 g, but this rate did not differ significantly from the rate of uterine rupture associated with birth weights < or = 4250 g (P = .1). CONCLUSION: A trial of labor after previous cesarean delivery may be a reasonable clinical option for pregnant women with suspected birth weights of > 4000 g, given that the rate of uterine rupture associated with these weights does not appear to be substantially increased when compared to lower birth weights. However, some caution may apply when considering a trial of labor in women with infants weighing > 4250 g. In these women with infants weighing > 4000 g, the likelihood of successful vaginal delivery, although lower than for neonates weighing < or = 4000 g, is still 60%.

OBJECTIVE: To examine the association between uterine rupture and oxytocin use in trial of labor after cesarean. METHODS: A case-control study was performed. Cases were all women with uterine ruptures who received oxytocin during a trial of labor after a single cesarean delivery within a 12-year period (n = 24). Four controls undergoing trial of labor after a single cesarean delivery were matched to each case by 500 g birth weight category, year of birth, and by induction or augmentation (n = 96). The study had an 80% power to detect a 40% increase in oxytocin duration or a 65% increase in total oxytocin dose. RESULTS: No significant differences were seen in initial oxytocin dose, maximum dose, or time to maximum dose. Although women with uterine ruptures had higher exposure to oxytocin as measured by mean total oxytocin dose (544 mU higher) and oxytocin duration (54 minutes longer), these differences were not statistically significant. Women with uterine rupture who received oxytocin were more likely to have experienced an episode of uterine hyperstimulation (37.5% compared with 20.8%, P =.05). However, the positive predictive value of hyperstimulation for uterine rupture was only 2.8%. CONCLUSION: Although no significant differences in exposure to oxytocin were detected between cases of uterine rupture and controls, the rarity of uterine rupture limited our power to detect small differences in exposure. In women receiving oxytocin, uterine rupture is associated with an increase in uterine hyperstimulation, but the clinical value of hyperstimulation for predicting uterine rupture is limited.

OBJECTIVE: To compare outcomes in women with prior cesareans delivering at or before 40 weeks' gestation with those delivering after 40 weeks. METHODS: We reviewed labor outcomes over 12 years at one institution for women with one prior cesarean and no other deliveries who had a trial of labor at term. We analyzed the rates of symptomatic uterine rupture and cesarean for term deliveries before or after 40 weeks and stratified for spontaneous and induced labor. Potential confounding by birth weight was controlled using logistic regression. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated. RESULTS: Of 2775 women with one prior scar and no other deliveries, 1504 delivered at or before 40 weeks and 1271 delivered after 40 weeks. For spontaneous labor, rupture rate at or before 40 weeks was 0.5% compared with 1.0% after 40 weeks (P =.2, adjusted OR 2.1, CI 0.7, 5.7). For induced labor, uterine rupture rates were 2.1% at or before 40 weeks and 2.6% after 40 weeks (P =.7, adjusted OR 1.1, CI 0.4, 3.4). For spontaneous labor, rate of cesareans during subsequent trials of labor at or before 40 weeks was 25% compared with 33.5% after 40 weeks (P =.001, adjusted OR 1.5, CI 1.2, 1.8). For induced labor, rate of cesareans during subsequent trials of labor at or before 40 weeks was 33.8% compared with 43% after 40 weeks (P =.03, adjusted OR 1.5, CI 1.1, 2.2). CONCLUSION: The risk of uterine rupture does not increase substantially after 40 weeks but is increased with induction of labor regardless of gestational age. Because spontaneous labor after 40 weeks is associated with a cesarean rate similar to that following induced labor before 40 weeks, awaiting spontaneous labor after 40 weeks does not decrease the likelihood of successful vaginal delivery.

OBJECTIVE: To relate interdelivery interval to risk of uterine rupture during a trial of labor after prior cesarean delivery. METHODS: We reviewed the medical records of all women who had a trial of labor after cesarean delivery over 12 years (July 1984 to June 1996). Analysis was limited to women with only one prior cesarean delivery and no prior vaginal deliveries who delivered term singletons and whose medical records included the month and year of the prior delivery. The time in months between the prior cesarean delivery and the index trial of labor was calculated, and the women were divided accordingly to permit comparison with respect to symptomatic uterine rupture. RESULTS: Two thousand four hundred nine women had trials of labor after one prior cesarean delivery and had complete data from the medical records. There were 29 uterine ruptures (1.2%) in the population. For interdelivery intervals up to 18 months, the uterine rupture rate was 2.25% (seven of 311) compared with 1.05% (22 of 2098) with intervals of 19 months or longer (P =.07). Multiple logistic regression was used to assess the risk of uterine rupture according to interdelivery interval while controlling for maternal age, public assistance, length of labor, gestational age at least 41 weeks, and oxytocin use. Women with interdelivery intervals of up to 18 months were three times as likely (95% confidence interval, 1.2, 7.2) to have symptomatic uterine rupture. CONCLUSION: Interdelivery intervals of up to 18 months were associated with increased risk of symptomatic uterine rupture during a trial of labor after cesarean delivery compared with that for longer interdelivery intervals.