Objective: To evaluate the effect of early amniotomy on mode of delivery and pregnancy outcome in comparison to a group of patients admitted with premature rupture of membranes at term.
Study design: The study population consists of all women (n=338) whose labor was induced by amniotomy, between the years 1988 to 1995. The comparison group were all women (n=1865) who were admitted with premature rupture of membranes during the same period.
Results: Cesarean section was significantly higher in the amniotomy group than in the comparison group (162 (47.9%) vs. 348 (18.7%), P<0.001). This significant difference was noted only for those who did not had a previous cesarean section (106 (42.4%) vs. 224 (13.8%), P<0.001). Non progressive labor during the first stage was threefold higher in the amniotomy group than in the control group (30.8% vs. 10.9%, P<0.001). Abnormal fetal heart rate patterns were detected during labor in 52 patients (15.4%) of amniotomy group, as compared to 141 cases (7.6%) in the control group (P<0.001). To assess the independent contribution of early amniotomy to having cesarean section in the present delivery, a multiple logistic model was used. Early amniotomy (odds ratio [OR] 3.07, 95% confidence interval [CI] 2.36-4.01), as well as a previous cesarean section (OR 5.04, 95% CI 3.90-6.52) and high parity (OR 1.07, 95% CI 1.03-1.26) were all found as independent risk factors for cesarean section.
Conclusions: Early amniotomy appears to be associated with an increased risk for cesarean section.