Chemical ripening of the cervix with intracervical application of sodium nitroprusside: a randomized controlled trial.

Nitric oxide (NO) has been found to be involved in the processes of cervical ripening. In a randomized, placebo-controlled study, cervical softening by an intracervical application of sodium nitroprusside, one of the most clinically potent and effective NO donor agents, was evaluated. A total of 36 primigravid women undergoing pregnancy termination between 9 and 12.5 weeks were enrolled. In one series, 18 patients were randomized to receive intracervically either placebo or 1\% nitroprusside gel (5 mg), followed by uterine evacuation 6 h after treatment. In another series, 18 patients received either placebo or 2\% nitroprusside gel (10 mg) into the cervical canal followed by uterine evacuation 3 h later. The cervical resistance, i.e. the force required to dilate the cervix from 3 to 10 mm, was the main outcome variable. It was recorded using a force sensing apparatus (dynamometer). Blood pressure was measured. Adverse events were recorded until 2 h after surgery. Women treated with both doses of nitroprusside gel showed values of cervical resistance significantly lower than those treated with placebo gel, at any tested diameter. No differences were found between subjects treated with the two different doses of nitroprusside. No significant consistent changes in blood pressure were induced by either dose of nitroprusside. No headaches were found in subjects treated with the NO donor. This study demonstrates that sodium nitroprusside applied into the cervical canal induces a rapid and significant softening of the cervix, thus reducing the force required to dilate it, compared with placebo-treated subjects. The chemical ripening of the cervix with sodium nitroprusside intracervical gel is an efficacious procedure in first-trimester pregnancy.