women with spontaneous onset of labor. Of those women receiving mifepristone, 54 percent had spontaneous onset of labor, compared with only 18.2 percent of those given a placebo. The interval between day 1 of treatment and the onset of labor for patients given mifepristone was 51.7 hours; for those on placebo it was 74.5 hours. In addition, the total dose of oxytocin required in mifepristone-treated patients was significantly lower than in those treated with placebo, although the cesarean section rate was equivalent. The evaluation of newborns by Apgar scores and measurement of umbilical vein pH levels showed no difference in outcome between mifepristone and placebo-treated patients. The authors concluded that mifepristone appeared to be a safe, efficient, and suitable induction agent for initiation of labor in women at term (Frydman et al., 1992).
It would be valuable in clinical practice to initiate labor more easily in post-term patients, as well as in women with medical conditions requiring relatively immediate (within two to four days) delivery. As mifepristone has been, and presumably will continue to be, given to women in late gestation, the opportunity to study any effects should be used. Prudence and caution dictate follow-up of infants born when labor is induced using antiprogestins. Assessments should include pulmonary, cardiac, and adrenal status of neonates as well as their later development and fertility potential. In addition, the early initiation of abundant lactation reported in the primate model suggests the need for studies in women to determine the impact of antiprogestins on lactation. The committee encourages dose-finding studies to determine the minimal dosage of antiprogestin necessary to induce labor.
Recommendation No. 12. The committee recommends studies to determine the minimal dose of antiprogestins necessary to induce labor. Studies in animal models (most likely the primates) should assess possible adverse outcomes on infants. Research is also needed to determine the effect of antiprogestins on maternal lactation.
Mifepristone is currently used with government approval in France, the United Kingdom, and Sweden. There are a variety of applications during pregnancy ranging from early first-trimester pregnancy termination to termination during second-trimester and even third-trimester labor induction (e.g., preeclampsia, post-term pregnancy, fetal demise). The application of mifepristone for cervical ripening at term, and for labor induction in late pregnancy when medical complications require it, has been tested and shows promise. Mifepristone appears to be effica-