Determinants of risk of spontaneous abortions in the first trimester of pregnancy.

Several factors, such as socioeconomic status, obstetrical and menstrual history, and contraceptive methods, have been associated with risk of spontaneous abortion. We conducted a hospital case-control study to analyze risk factors for spontaneous abortion during the first trimester. Cases were 782 women admitted for spontaneous abortion. Controls included 1,543 women who gave birth at term in the same hospitals. Adjusted odds ratios (ORs) for spontaneous abortion were 0.9 and 0.6, respectively, for women reporting 7-11 and > or = 12 years of schooling, compared with women reporting < 7 years of education. A history of pelvic inflammatory disease increased the odds ratio fivefold [OR = 5.1; 95% confidence interval (CI) = 1.0-26.2]. The OR for spontaneous abortion was 1.7 (95% CI = 1.4-2.1) in women reporting previous spontaneous abortions.