Background: Preparing the cervix prior to surgical abortion is intended to make the procedure both easier and safer. Options for cervical preparation include osmotic dilators and pharmacologic agents. Many formulations and regimens are available, and recommendations from professional organizations vary for the use of preparatory techniques in women of different ages, parity or gestational age of the pregnancy.

Objectives: To determine whether cervical preparation is necessary in the first trimester, and if so, which preparatory agent is preferred.

Search strategy: We searched Cochrane, Popline, Embase, Medline and Lilacs databases for randomised controlled trials investigating the use of cervical preparatory techniques prior to first trimester surgical abortion. In addition, we hand-searched key references and contacted authors to locate unpublished studies or studies not identified in the database searches.

Selection criteria: Randomised controlled trials investigating any pharmacologic or mechanical method of cervical preparation, with the exception of nitric oxide donors (the subject of another Cochrane review), administered prior to first trimester surgical abortion were included. Outcome measures must have included the amount of cervical dilation achieved, the procedure duration or difficulty, side-effects, patient satisfaction or adverse events to be included in this review.

Data collection and analysis: Trials under consideration were evaluated by considering whether inclusion criteria were met as well as methodologic quality. Fifty-one studies were included, resulting in 24 different cervical preparation comparisons. Results are reported as odds ratios (OR) for dichotomous outcomes and weighted mean differences for continuous data.

Main results: When compared to placebo, misoprostol (400-600 microg given vaginally or sublingually), gemeprost, mifepristone (200 or 600 mg), prostaglandin E and F(2alpha) (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 microg oral or 800 microg 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 microg 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 E(2) andF(2alpha)) were associated with high rates of gastrointestinal side-effects and unplanned pregnancy expulsions. Few studies reported women's satisfaction with cervical preparatory techniques.

Authors' conclusions: 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, 400microg administered either vaginally or sublingually, are the most effective methods of cervical preparation.