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The effects of several family and embryonic factors on the abortion pattern in a rural Mediterranean population (La Alta Alpujarra Oriental, Southeast Spain) were analyzed from interview data on 3163 pregnancies from the first half of the twentieth century. No significant differences in spontaneous abortion rates were detected between endogamous and exogamous couples. The abortion pattern of this population is characterized mainly by family and embryonic factors. High rates of early abortions were significantly associated with maternal age and pregnancy order, and parental consanguinity was linked with a notable decrease of abortion frequency during the earlier stages of pregnancy. A tendency toward a higher risk for abortion was also confirmed for twinship of the fetus. The interactions identified between abortion risk and maternal age, pregnancy order, and inbreeding emphasize the important contribution of sociodemographic factors to prereproductive mortality in human populations.