labor during the second and third trimesters of pregnancy. A variety of prostaglandins have been shown to induce uterine contractions in both second- and third-trimester pregnancies. The experience with mifepristone in first-trimester pregnancy termination suggested that mifepristone treatment sensitizes the myometrium to the action of prostaglandins, thereby reducing the amount of prostaglandin necessary to induce expulsion. This led to the hypothesis that antiprogestins might be useful in termination of pregnancies during the second and third trimesters as well.
Currently, second-trimester pregnancy termination is available in the United States by dilation and evacuation (D&E), by intra-amniotic saline injection, intra-amniotic prostaglandin F2a, or prostaglandin E2 vaginal suppositories. These procedures are used for elective pregnancy termination in the second trimester, including termination of pregnancies where fetal genetic or structural abnormalities have been documented. Prostaglandin termination of second-trimester pregnancies requires two to three days of inpatient hospital stay with significant discomfort. The alternative surgical procedure of D&E, although widely used, requires highly skilled technical ability, which may not be available in all clinical settings. A series of clinical trials has been performed to study the efficacy of mifepristone treatment before prostaglandin administration for second-trimester pregnancy termination to determine whether smaller doses of prostaglandin following mifepristone are as effective as larger doses of prostaglandin alone. All of these studies (Ulmann and Silvestre, Appendix B6) have suggested that treatment with mifepristone before prostaglandin, whether gemeprost, sulprostone, or PGE2, decreases significantly the level of prostaglandin needed to complete an abortion and shortens the time interval from administration to abortion. Given the multiday hospital admission required for a second-trimester prostaglandin abortion, as well as the high level of discomfort for the woman, the ability of antiprogestins to shorten the duration of hospitalization by one day would be significant. Other studies comparing the effects of antiprogestins with those of laminaria tents (Dilapan®) in gemeprost-induced second-trimester abortion documented that the use of mifepristone resulted in a significantly shorter induction-to-abortion interval than did the Dilapan (Thong and Baird, 1992).
Recommendation No. 11. With regard to second-trimester abortion, the committee recommends conducting clinical trials in the United States to compare the established surgical procedure of dilation and evacuation (D&E) both to antiprogestins in combination with prostaglandins and to prostaglandins used alone. Such trials should clarify the optimal dose of antiprogestin and prostaglandin for this use,