Objective: To determine the mean umbilical arterial (UA) pH and incidence of UA pH less than 7.10 in infants born to women with histories of prior cesareans.
Methods: Three groups were studied retrospectively. Elective repeat cesarean (n = 113), cesarean after labor (n = 58), and successful vaginal birth after cesarean (VBAC) (n = 135). Comparisons were made across all groups and between elective cesarean and patients who labored.
Results: The mean UA pH values were 7.22 for elective cesarean, 7.20 for cesarean after labor, and 7.24 for VBAC (P = .04). Among the patients who had elective cesareans, 11 (10%) of 110 had a UA pH of less than 7.10, compared with 11 (6%) of 185 among patients who labored, P = .25, odds ratio 0.6, 95% confidence interval 0.22, 1.47.
Conclusion: Comparing neonates who underwent trials of labor with those delivered by cesarean, there was no significant difference in the percentage with UA pH values less than 7.10, suggesting vaginal delivery after previous cesarean does not have a deleterious effect on umbilical cord gases. However, our sample size precluded us from examining lower cut points for UA pH, which are of greater clinical significance. Therefore, these results should be interpreted cautiously until confirmed by other studies.
(C) 1998 The American College of Obstetricians and Gynecologists