Trial of labor after 40 weeks' gestation in women with prior cesarean

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 wo men with one prior cesarean and no other deliveries who had a trial of labo r at term. We analyzed the rates of symptomatic uterine rupture and cesarea n for term deliveries before or after 40 weeks and stratified for spontaneo us and induced labor. Potential confounding by birth weight was controlled using logistic regression. Adjusted odds ratios (OR) and 95% confidence int ervals (CI) were calculated. Results: Of 2775 women with one prior scar and no other deliveries, 1504 de livered at or before 40 weeks and 1271 delivered after 40 weeks. For sponta neous 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 wee ks (P = .7, adjusted OR 1.1, CI 0.4, 3.4). For spontaneous labor, rate of c esareans during subsequent trials of labor at or before 40 weeks was 25% co mpared 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 o r before 40 weeks was 33.8% compared with 43% after 40 weeks (P = .03, adju sted OR 1.5, CI 1.1, 2.2). Conclusion: The risk of uterine rupture does not increase substantially aft er 40 weeks but is increased with induction of labor regardless of gestatio nal age; Because spontaneous labor after 40 weeks is associated with a cesa rean rate similar to that following induced labor before 40 weeks, awaiting spontaneous labor after 40 weeks does not decrease the likelihood of succe ssful vaginal delivery. (C) 2001 by The American College of Obstetricians a nd Gynecologists.