Risk factors of early spontaneous abortions among Japanese: a matched case-control study

Abstract

No epidemiological studies have examined risk factors for early spontaneous abortions among Japanese women. In this matched case–control study, we investigated the associations of reproductive, physical, and lifestyle characteristics of women and their husbands with early spontaneous abortion <12 weeks of gestation. Information was collected through medical records for 430 cases of early spontaneous abortion and 860 controls of term delivery. Two controls were individual-matched to one case according to maternal age (±3 years) and calendar year of events (either early spontaneous abortion or delivery). Multivariable conditional odds ratios (ORs) and 95% confidence interval (CI) were calculated with conditional logistic-regression. The risk of early spontaneous abortions was higher for women with a past history of early spontaneous abortions; OR was 1.98 (95% CI: 1.35, 2.89) for one previous spontaneous abortion, 2.36 (95% CI: 1.47, 3.79) for two, and 8.73 (95% CI: 5.22, 14.62) for three or more. Other factors also influence risk; an OR of 2.39 (95% CI: 1.26, 4.25) was found for women who smoked, and 1.65 (95%CI: 1.17, 2.35) for women working outside the home. Our finding suggests that for Japanese women, smoking and working may be important public health issue targets for the prevention of early spontaneous abortions.