Maternal atopy and changes in parity

Abstract

Atopic women tend to have fewer children, although atopy may favour conception. 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. 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. 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). 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.