A FOLLOW-UP-STUDY OF ENVIRONMENTAL AND BIOLOGIC DETERMINANTS OF FERTILITY AMONG 430 DANISH FIRST-PREGNANCY PLANNERS - DESIGN AND METHODS

This paper presents design and methods of a follow-up study of fecunda bility (defined as the probability of conception during one menstrual cycle) in first-pregnancy planners, We recruited 430 couples by postal letter among 52,255 members of four trade unions. Couples without ear lier reproductive experience were enrolled when they discontinued cont raception and were followed in six complete menstrual cycles or until a pregnancy was recognized. Data included daily recordings of coitus a nd menstrual bleeding, Blood, semen, and urine specimens were collecte d to assess endocrine profile, semen quality, occult embryonal loss, a nd occupational exposures, Information was obtained about 1661 menstru al cycles (94% of expected). The proportion of couples obtaining a cli nical pregnancy during 6 months of follow-up was 65%, and the average probability to obtain a pregnancy across all cycles was 16% (95% CI 14 -18%), Among all conceptions the proportion of early embryonal loss wa s 17% (95% CT 12-22%). This study demonstrates the feasibility of a pr ospective study of fertility and that the established study base can p rovide useful information on environmental risk to subfertility. (C) 1 998 Elsevier Science Inc.