Vaginal misoprostol for pre-abortion cervical priming: is there an optimalevacuation time interval?

Objective To determine the optimal evacuation time interval in the use of v aginal misoprostol for cervical priming before first trimester termination of pregnancy. Design Prospective double-blind randomised study. Setting Fertility Control Centre, National University Hospital, Singapore. Methods Sixty healthy nulliparous women requesting legal termination of pre gnancy between 6 and 11 weeks of gestation were randomly allocated to eithe r the 400 mu g or 600 mu g misoprustol group, vacuum aspiration was perform ed after three hours in the 400 mu g group and at the end of two hours in t he women given 600 mu g misoprostol. Using Hegar's dilator, degree of cervi cal dilatation before operation was measured. Other parameters assessed inc luded the amount of additional dilatation required (if < Hegar 8), pre-oper ative and intra-operative blood loss, and associated side effects. Results For the 600 mu g group, only five women (16.7%) achieved a cervical dilatation of greater than or equal to 8 mm, compared with 28 women (93.3% ) in the 400 mu g group. Using the 400 mu g misoprostol group as a baseline , the odds ratio was 0.014 (95% CI 0.003-0.080) for 600 mu g for successful pre-operative cervical dilatation of greater than or equal to 8 mm. The me an cen ical dilatation for 400 and 600 mu g misoprostol was 8.1 mm and 6.6 mm, respectively (P < 0.001). Despite the shorter evacuation time interval of two hours, the 600 mu g dose was associated with an increase in side eff ects such as vaginal bleeding, abdominal pain and a fever of > 38.0 degrees C. However, other than abdominal pain. no significant differences in the f requency of these side effects were shown. Conclusion Use of 400 mu g misoprostol with a minimal evacuation time inter val of three hours still appears the optimal dosage and evacuation time for cervical priming before first trimester termination of pregnancy.