[Smoking reduces the biological capacity of conception. Results from a European multicenter study. The European Study...

The aim of the study was to examine the impact on subfecundity of male and female smoking at the start of a couple's waiting time to a planned pregnancy. Two types of designs were applied: a population based sample of women aged 25-44 years of age and a consecutive sample of pregnant women. Both studies were conducted within well-defined geographical regions in a number of European countries and data were collected by personal interviews in the population-based sample and by interview or self-administered questionnaires in the pregnancy study. A total of 10,665 couples participated in the study. Data on possible risk factors for infertility and subfecundity were collected at the start of the pregnancy planning, and fecundity was estimated by using time from the beginning of unprotected intercourse to a pregnancy, which survived at least 20 gestational weeks. Only couples who planned a pregnancy were included in the analyses. The results showed remarkably coherent associations between female smoking and subfecundity in each individual country and in all countries put together. In the population sample the odds ratio for subfecundity in the first pregnancy was 1.7 (95% c.l. 1.3-2.1 at the upper level of tobacco consumption) and during the most recent waiting time to pregnancy the odds ratio was 1.6 (95% c.l. 1.3-2.1). Results based on the pregnancy sample were similar with an odds ratio of 1.7 (95% c.l. 1.3-2.3). No significant association was found between male smoking and the couple's fecundity.