Abstract: 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. 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.

Plain-language summary: We did computer searches for all published randomized trials that compared different methods of cervical preparation before second-trimester D&E and we found six studies that met our criteria. All of the methods compared were different from one another, thus it was not possible to combine data from multiple studies. We looked at how these preparation methods compared with respect to safety, procedure time, need for additional dilation, ability to perform the procedure, and patient and provider acceptability. We found that all methods reviewed were safe. Certain dilators called laminaria appeared to result in more cervical opening (dilation) than the prostaglandin medications, however no difference was seen between dilators and prostaglandins with respect to safety, length of procedure, or the ability to complete the procedure. We found that when mifepristone, a medication that blocks the action of a hormone called progesterone, was used with a prostaglandin called misoprostol that many women ended up expelling the pregnancy before their desired surgical procedure. Due to this increased rate of expulsions prior to planned D&E, we feel that the combination of mifepristone and misoprostol should not be used for cervical preparation when women are desiring a surgical procedure instead of an induction. We found that one day of cervical preparation is just a good as two days and that same-day cervical preparation appears to be safe in the early part of the second trimester. We believe that more research is needed in the area of same-day cervical preparation as it is much easier for women to have a one-day instead of a multiple day procedure. We also think more research is needed in the area of combining prostaglandins with dilators as this may improve the possibility of conducting same-day procedures later into the second trimester.