PATERNAL AND MATERNAL SMOKING-HABITS BEFORE CONCEPTION AND DURING THEFIRST-TRIMESTER - RELATION TO SPONTANEOUS-ABORTION

PURPOSE: This study examined the association between maternal smoking before and during the first trimester of pregnancy and spontaneous abo rtion. METHODS: We have been conducting a hospital-based case-control study on risk factors for spontaneous abortion in the greater Milan ar ea. We collected information from 782 cases of spontaneous abortions a nd 1543 controls (women who delivered at term healthy infants). RESULT S: With respect to never smokers, the odds ratio (OR) were 0.7 (95%, c onfidence interval (CI), 0.5-1.0) for women who quit smoking and 1.3 ( 95% CI, 1.0-1.6) for those who continued during pregnancy. Women who s moked more than 10 cigarettes/day in the first trimester were at incre ased risk of miscarriage, with an OR of 1.4 (95% CI, 1.0-2.1). No rela tionship was evident between the number of cigarettes smoked before co nception and the risk of abortion. Likewise, no association emerged be tween paternal smoking and miscarriage. Moreover, no significant inter action or modification effect was obtained when strata of age and othe r major characteristics were investigated. CONCLUSIONS: The risk of ab ortion associated with cigarette smoking during the first trimester of pregnancy was measurable and noticeable in this population, and accou nted for 9% (95% CI, 6-13%) of all cases. The increased risk of sponta neous abortion in women smoking during pregnancy is a further reason t o encourage pregnant women to quit. (C) 1998 Elsevier Science Inc.