Nitric oxide donors induce ripening of the human uterine cervix: a randomised controlled trial

Objective To determine whether nitric oxide donors can induce cervical ripening before surgical termination of pregnancy in the first trimester. Design Prospective, randomised controlled trial. Setting Department of Obstetrics and Gynaecology, Royal Infirmary, Glasgow. Participants Forty-eight primigravid women undergoing surgical termination of pregnancy before 12 weeks of gestation. Methods The women were randomised to receive per vaginam before surgery either the nitric oxide donor isosorbide mononitrate, the nitric oxide donor glyceryl trinitrate, the prostaglandin analogue gemeprost, or no treatment. Main outcome measures The cumulative force required to dilate the cervix to 8 mm was measured objectively and the cervical diameter before surgical dilatation was recorded. Results Following isosorbide mononitrate or gemeprost, a lower cumulative force was required to dilate the cervix to 8 mm and a higher cervical diameter before dilatation was recorded. Pretreatment with glyceryl trinitrate reduced the cumulative force required to dilate the cervix but had no effect on cervical diameter. Conclusions Like the prostaglandin analogue gemeprost, the nitric oxide donors isosorbide mononitrate and glyceryl trinitrate can effect cervical ripening. Nitric oxide donors may provide an alternative to prostaglandins for cervical ripening before surgical procedures in the first trimester.