Background: Abortion during the second trimester of pregnancy accounts for 10-15% of abortions performed worldwide. Dilation and evacuation (D&E) is the preferred method of second-trimester abortion in most parts of the developed world. Cervical preparation is recommended for dilation and curettage (D&C) after 12 weeks gestation and is standard practice for D&E beyond 14 weeks gestation. Prostaglandins, osmotic dilators, and Foley balloon catheters have been used and studied as cervical preparation prior to second-trimester D&E. However, no consensus exists as to which cervical preparation method is superior with regards to safety, procedure time, need for additional dilation, ability to perform the procedure, or patient and provider acceptability. Despite the fact that the advent of osmotic dilation has improved the safety of the D&E procedure during the second trimester, it is unclear whether a certain type of osmotic dilator is superior to another or whether osmotic dilation with adjuvant prostaglandin is superior to osmotic dilation alone or to prostaglandins alone.

Objectives: This review evaluates cervical preparation methods for second-trimester surgical abortion with respect to differences in procedure time, dilation achieved, need for additional dilation, complications, ability to complete the procedure, patient pain scores, and patient and provider acceptability and satisfaction.

Search strategy: We searched for trials of cervical preparation prior to second-trimester D&E.

Selection criteria: We included all randomized controlled trials that compared osmotic, mechanical, antiprogesterone, prostaglandin, or other medical agents of cervical preparation for second-trimester surgical abortion from 14-24 weeks of gestation.

Data collection and analysis: Data were abstracted by two authors and data entry was verified by a third author. Mean difference and Peto Odds Ratio were calculated.

Main results: Osmotic dilators were found to be superior to prostaglandins with respect to cervical dilation throughout the second trimester and with respect to procedure time within the early second trimester. Addition of prostaglandins to osmotic dilators was not found to increase cervical dilation, except after 19 weeks gestation, however, no impact was seen on procedure time. Addition of Mifepristone to misoprostol was found to improve cervical dilation, yet increase procedure time and frequency of pre-procedural expulsions. Two-day cervical preparation was found to produce greater cervical preparation than one-day, but had no impact on procedure time. Serious complication rates or ability to complete the procedure did not differ significantly between any of the preparation methods reviewed.

Authors' conclusions: Cervical preparation with osmotic dilators and/or misoprostol before second-trimester D&E is safe and effective. Osmotic dilators appear to provide superior cervical dilation when compared to prostaglandins alone or when combined with prostaglandins, however this difference in cervical dilation does not appear to result in differences in procedure time or complication rates. There does not appear to be clear clinical benefit from two days of cervical preparation compared to one-day prior to second-trimester D&E below 19 weeks gestational duration. Mifepristone plus misoprostol was associated with high rates of pre-procedural expulsions and does not appear to be a useful method of cervical preparation before second-trimester dilation and evacuation. Same-day procedures appear to be a safe and reasonable option in the early second trimester, however, more research is needed to assess the effectiveness and safety of same-day procedures in the later second trimester.