Maternal atopy and changes in parity

Background: Atopic women tend to have fewer children, although atopy may favour conception. Objective: To assess whether atopy is associated with the number of new births and whether changes in parity are associated with a change in atopy in a cohort of young women. Methods: Women had atopy (defined as the presence of serum-specific IgE against common aeroallergens) measured in the European Community Respiratory Health Study during the years 1991-92 (n = 4580). About 9 years later, 2844 (62.1%) were recontacted and 2414 (52.7%) had atopy measured again. Results: Atopic women had fewer children at baseline than non-atopic women but the association disappeared at the end of the follow-up. Atopy tended to increase parity during the follow-up, but in a non-statistically significant way (relative risk = 1.08; 0.86-1.35, after adjusting for number of children at baseline, age, length of follow-up, education or social class). Prevalence of atopy during the follow-up changed by the same magnitude whatever the birth cohort and the change in the number of children (P for interaction >0.7). Conclusion: Atopic women did not have a significantly higher fertility rate but they may postpone having their first child compared with non-atopic women. We are unable to confirm the hypothesis that atopy in women may decrease with successive pregnancies.