Abortion during the second trimester of pregnancy accounts for 10-15% of abortions performed worldwide (Finer 2005; Stat. Service. 2005; WHO 1997). Surgical evacuation, called dilation and evacuation (D&E), is the preferred method of second-trimester abortion, as opposed to induction of labor, in most developed countries where D&E and medical methods are both available (Lohr 2008; RCOG 2004). In order to perform a D&E, surgical instruments must pass through the cervix, the opening to the uterus, into the uterus. In order for these instruments to pass through the cervix safely, the cervix must be opened prior to the procedure. This process of opening the cervix prior to a D&E is called cervical preparation and can be done with medications or with small rod-like devices that are placed inside the cervix. The most commonly used medications for cervical preparation are called prostaglandins. These medications can be taken orally or placed in the vagina or the cheeks and need to be taken several hours before the procedure. They work by softening, thinning, and opening the cervix so that at the time of the procedure it is possible to further open the cervix if needed and to place the instruments through the cervix into the body of the uterus. The small-rod like devices used for cervical preparation are called cervical dilators. Dilators are placed inside the cervix several hours before the procedure or even a day or two before the procedure. In general, dilators work by absorbing moisture from the cervix which causes the dilators to swell and get larger. As the diameter of these dilators expands the dilator puts radial pressure on the cervical walls and causes the cervix to open.
There are many options of what to use for cervical preparation before a second-trimester D&E. These methods have different side effects and take varying amounts of time from about four hours prior to the procedure to two days before. Since there is no clear consensus as to what cervical preparation method is best for preparing the cervix for a second-trimester D&E, we reviewed all published, randomized trials that compared different methods of cervical preparation before second-trimester D&E, defined as between 14 and 24 weeks of pregnancy.
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.