Two dosing regimens for preinduction cervical priming with intravaginal dinoprostone pessary: a randomised clinical trial

Objective To compare the efficacy within 24 hours of a three-times-a-day intensive dosing regimen with a standard once daily dosing regimen using dinoprostone vaginal pessary in preinduction cervical priming. Design Randomised controlled trial. Setting Department of Obstetrics and Gynaecology, Singapore General Hospital. Participants One hundred singleton term primigravidae with cephalic presentation with unfavourable cervical scores (Bishop score less than or equal to 5) requiring induction of labour. Methods Eligible women were randomly assigned the standard regimen (3000 mu g dinoprostone [Prostin, Upjohn, Crawley, UK] once daily) or an intensive regimen (3000 mu g dinoprostone given sequentially three times daily four hours apart) for cervical priming until successful priming (Bishop score of greater than or equal to 6) or the onset of active labour occurred. Main outcome measures Number of women whose cervices were ripened successfully or who entered active labour within 24 hours of starting cervical priming, priming to induction interval, and priming to delivery interval. Results Forty-nine women were assigned to the standard regimen and 51 to the intensive regimen. The median number (range) of dinoprostone pessaries used was two (one to seven) in the standard regimen and three (one to nine) in the intensive regimen. Forty-two women (82.4%) who underwent the intensive regimen achieved successful cervical ripening or active labour within 24 hours, compared with 21 assigned to standard regimen (OR 6.2, 95% CI 2.3-17.4). This difference was statistically significant. The median intervals from priming to induction, and from priming to delivery, were also statistically significantly shorter in women treated with the intensive regimen. Thirty-five women (68.63%) assigned the intensive regimen experienced pain, compared with 21 (42.86%) in the standard regimen (OR 2.92, 95% CI 1.19-7.21), with two and one women in the respective regimens requiring opiate analgesics. Five women with oligohydramnios had transient cardiotocographic abnormalities during priming with the intensive regimen, none of which required immediate intervention, and the babies were born in good condition. There were no cases of uterine hypertonus and the outcomes of labour were similar for women from both regimens. Conclusions Preinduction cervical priming with the intensive dosing regimen improves the chances of successful ripening within 24 hours for primigravidae with unfavourable cervical scores at full term singleton pregnancies, and shortens the interval from priming to induction, and priming to delivery. This regimen may be more cost effective by shortening the period of hospital stay. The overall incidence of adverse reactions to the mother and fetus during priming was low. However, close fetal surveillance must be maintained, particularly in pregnancies complicated with oligohydramnios.