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The MFMU cesarean registry: Previous preterm low transverse cesarean delivery and risk of subsequent uterine rupture

      Objective

      Preterm low transverse cesarean delivery (pLTCD) is often performed on an unlabored uterus with a poorly developed lower uterine segment, potentially leading to an unsuspected incision in the contractile portion of the uterus. We sought to determine if a previous pLTCD was associated with an increased risk of subsequent uterine rupture.

      Study design

      Secondary analysis of a prospective observational study performed at 19 tertiary care centers of all women with singleton gestations and a previous cesarean from 1999 to 2002. Women with a previous pLTCD were compared to women with a previous term LTCD. Women who had both were included in the preterm group.

      Results

      41,381 women had a previous LTCD. Of those 5,842 had at least one prior preterm and 35,539 had only previous term LTCD. Women who had a previous pLTCD had an increased risk of subsequent uterine rupture (0.58% vs. 0.28%; p=0.0002, OR: 2.05 [95% CI: 1.39-3.02]). When women who had an elective LTCD were removed (total n=26,462) women with a pLTCD were still more likely to have a uterine rupture (0.79% vs. 0.46%; p= 0.005, OR: 1.72 [95% CI: 1.17-2.54]). Among 15,901 women undergoing a trial of labor (TOL), this trend persisted but did not reach statistical significance (1.0 vs. 0.68%; p=0.08, OR: 1.48 [95% CI: 0.95-2.29]). Multivariate analysis revealed women with a previous pLTCD to be at increased risk of uterine rupture (p=0.04, OR: 1.59, 95% CI: 1.01-2.50), after controlling for oxytocin use, ≥2 prior LTCDs, LTCD within two years, and preterm delivery in the current pregnancy. The risk of subsequent uterine rupture did not change with decreasing birthweight at prior LTCD (p=0.9). Women with a previous pLTCD and a subsequent term TOL were at the highest risk for uterine rupture at a rate of 1.18%.

      Conclusion

      Women with a previous pLTCD are at an increased risk for uterine rupture in a subsequent pregnancy when compared with those who have had a previous term LTCD.