Risk of Uterine Rupture and Placenta Accreta With Prior Uterine Surgery Outside of the Lower Segment

OBJECTIVE: Women with a prior myomectomy or prior classical cesarean delivery often have early delivery by cesarean because of concern for uterine rupture. Although theoretically at increased risk for placenta accreta, this risk has not been well-quantified. Our objective was to estimate and compare the risks of uterine rupture and placenta accreta in women with prior uterine surgery. METHODS: Women with prior myomectomy or prior classical cesarean delivery were compared with women with a prior low-segment transverse cesarean delivery to estimate rates of both uterine rupture and placenta accreta. RESULTS: One hundred seventy-six women with a prior myomectomy, 455 with a prior classical cesarean delivery, and 13,273 women with a prior low-segment transverse cesarean delivery were evaluated. Mean gestational age at delivery differed by group (P<.001), prior myomectomy (37.3 weeks), prior classical cesarean delivery (35.8 weeks), and low-segment transverse cesarean delivery (38.6 weeks). The frequency of uterine rupture in the prior myomectomy group (P-MMX group) was 0% (95% confidence interval [CI] 0-1.98%). The frequency of uterine rupture in the low-segment transverse cesarean delivery group (LTC group) (0.41%) was not statistically different from the risk in the P-MMX group (P>.99) or in the prior classical cesarean delivery group (PC group) (0.88%; P=.13). Placenta accreta occurred in 0% (95% CI 0-1.98%) of the P-MMX group compared with 0.19% in the LTC group (P>.99) and 0.88% in the PC group (P=.01 relative to the LTC group). The adjusted odds ratio for the PC group (relative to LTC group) was 3.23 (95% CI 1.11-9.39) for uterine rupture and 2.09 (95% CI 0.69-6.33) for accreta. The frequency of accreta for those with previa was 11.1% for the PC group and 13.6% for the LTC group (P>.99). CONCLUSION: A prior myomectomy is not associated with higher risks of either uterine rupture or placenta accreta. The absolute risks of uterine rupture and accreta after prior myomectomy are low. (Obstet Gynecol 2012;120:1332-37) DOI: http://10.1097/AOG.0b013e318273695b