Spontaneous abortion rate in patients with endometriosis treated with progesterone.

Several reports suggest that women with endometriosis have a higher risk of spontaneous abortions when left untreated; however, these studies did not control for the presence of possible luteal phase defects. This study was designed to document the frequency of spontaneous abortions in women with endometriosis and ovulation defects treated prophylactically with progesterone, compared with similar patients without endometriosis. All the women had late luteal phase endometrial biopsies dating perfectly normal. Our findings show an increase in the rate of spontaneous abortions (25.7%) in women with endometriosis as compared with the entire group (3.8%). However, when the result for the group with endometriosis is compared with the subgroup of patients at diagnostic laparoscopy not showing endometriosis, the results are similar (30%). We conclude that when properly matched groups are compared, there is no increased risk of spontaneous abortions in women with endometriosis. Since we perform laparoscopies only in women failing to conceive after a reasonable number of seemingly normal cycles, the apparently high incidence of abortions in this group may be secondary to other factors that not only may lengthen the time needed for conception but also increase the abortion risk after conception.