We included nine studies involving 766 participants. There were no serious complications (infection requiring antibiotic treatment, blood transfusion, complications requiring unintended operation, cervical injury, uterine perforation, death or serious morbidity) in the trials included.
NO donors were more effective in cervical ripening comparing with placebo or no treatment. Baseline cervical dilatation before the procedure was higher in NO donors group (mean difference 0.30, 95% CI 0.01, 0.58) The cumulative force required to dilate the cervix to 8 mm (mean difference -4.29, 95% CI -9.92, 1.35), headache (RR 1.73, 95% CI 0.86, 3.46), abdominal pain (RR 0.87, 95% CI 0.50, 1.50) or patient satisfaction (RR 0.95, 95% CI 0.84, 1.07) were not different. More nausea and vomiting occurred in the women who received a NO donor (RR 2.62, 95% CI 1.07, 6.45).
NO donors were inferior to prostaglandins for cervical ripening. The cumulative force required to dilate the cervix to 8-9 mm was higher (mean difference 13.12, 95% CI 9.72, 16.52) and baseline cervical dilatation was less (mean difference -0.73, 95% CI -1.01, -0.45) in the NO donor group. Side effects including headache (RR 5.13, 95% CI 3.29, 8.00), palpitation (RR 3.43, 95% CI 1.64, 7.15), dizziness (RR 3.29, 95% CI 1.46, 7.41) and intraoperative blood loss (mean difference 33.59 ml, 95% CI 24.50, 42.67) were also higher. However, abdominal pain (RR 0.33, 95% CI 0.25, 0.44) and vaginal bleeding (RR 0.14, 95% CI 0.07, 0.27) was less in the NO donor group. Patient satisfaction was not different.
One trial compared a NO donor with a NO donor plus prostaglandin. The cumulative force required to dilate the cervix to 8 mm was higher (mean difference 14.50, 95% CI 0.50, 28.50) in the NO donor group. There was no difference in headache (RR 0.88, 95% CI 0.38, 2.00), abdominal pain (RR 0.14, 95% CI 0.02, 1.07) or intraoperative blood loss (mean difference -50, 95% CI -164.19, 64.19).
