Increased rate of endometriosis and spontaneous abortion in an in vitro fertilization program: no correlation with epidemiological factors.

Background. There are conflicting data concerning endometriosis and spontaneous abortion (SAB). The aim of the present study was to evaluate if there was any association between endometriosis and SAB. Moreover, we investigated risk factors in women with endometriosis and SAB. Methods. The medical files of 457 married women with endometriosis and 200 infertile women without endometriosis were studied retrospectively. All cases were diagnosed by laparoscopy. Data concerning demographic variables and menstrual characteristics were recorded from 226 women with endometriosis, which were divided into two groups. Group 1 included 126 cases with endometriosis and SAB, and Group 2 comprised 100 parous women with endometriosis and without SAB. Statistical comparisons between groups were made using the chi(2) test and odds ratios (OR) and 95% confidence intervals (CI). Results. The proportion of SAB was significantly higher in women with endometriosis than in infertile women without endometriosis (126/457 (27.6%) vs. 36/200 (18.0%); OR = 1.7, 95% CI 1.1 = 2.6; p = 0.01). The frequency of nulligravid women was significantly higher in women with endometriosis than in the control group (OR= 1.9, 95% CI 1.4-2.81; p = 0.001). Mean age, age at onset of endometriosis, race, height, weight, body mass index, medical history of allergies, and family histories of endometriosis and cancer were similar in women with endometriosis and SAB and in parous women with endometriosis but without SAB. Moreover, the two groups were similar in age at menarche, length of cycle, duration and amount of flow, and the severity of disease. The incidence of infertility was significantly higher in women with SAB (p < 0.001). Conclusion. These data suggest but do not prove that the risk of SAB is increased in women with endometriosis. The epidemiological risk factors of endometriosis are not associated with an increase in the abortion rate.