Abstract: When compared to placebo, misoprostol (400-600 µg given vaginally or sublingually), gemeprost, mifepristone (200 or 600 mg), prostaglandin E and F2α (2.5 mg administered intracervically) demonstrated larger cervical preparation effects. When misoprostol was compared to gemeprost, misoprostol was more effective in preparing the cervix and was associated with fewer gastrointestinal side-effects. For vaginal administration, administration 2 hours prior was less effective than administration 3 hours prior to the abortion. Compared to oral misoprostol administration, the vaginal route was associated with significantly greater initial cervical dilation and lower rates of side-effects; however, sublingual administration 2-3 hours prior to the procedure demonstrated cervical effects superior to vaginal administration. When misoprostol (600 µg oral or 800 µg vaginal) was compared to mifepristone (200 mg administered 24 hours prior to procedure), misoprostol had inferior cervical preparatory effects. Compared to day-prior laminaria tents, 200 or 400 µg vaginal misoprostol showed no differences in the need for further mechanical dilation or length of the procedure; similarly, the osmotic dilators Lamicel and Dilapan showed no differences in cervical ripening when compared to gemeprost, although gemeprost had cervical effects which were superior to laminaria tents. Older prostaglandin regimens (sulprostone, prostaglandin E2 and F2α) were associated with high rates of gastrointestinal side-effects and unplanned pregnancy expulsions. Few studies reported women's satisfaction with cervical preparatory techniques. Modern methods of cervical ripening are generally safe, although efficacy and side-effects between methods vary. Reports of adverse events such as cervical laceration or uterine perforation are uncommon overall in this body of evidence and no published study has investigated whether cervical preparation impacts these rare outcomes. Cervical preparation decreases the length of the abortion procedure; this may become increasingly important with increasing gestational age, as mechanical dilation at later gestational ages takes longer and becomes more difficult. These data do not suggest a gestational age where the benefits of cervical dilation outweigh the side-effects, including pain, that women experience with cervical ripening procedures or the prolongation of the time interval before procedure completion. Mifepristone 200 mg, osmotic dilators and misoprostol, 400µg administered either vaginally or sublingually, are the most effective methods of cervical preparation.

Plain-language summary: This review found that cervical preparation decreased the length of time necessary for an abortion procedure, but did not seem to decrease rates of uncommon abortion complications. The medication called misoprostol worked better with less side-effects than other similar medications. Misoprostol is most effective with the least side-effects when placed in the vagina, but when placed under the tongue it is equally effective. Another drug called mifepristone worked better than misoprostol; however, it is more expensive to use. All methods of preparation take at least 2-3 hours or more to work. The review could not determine whether women preferred one method best.