Maternal atopy and the number of offspring: is there an association?

We investigated the association between maternal atopy and the number of offspring. In a population- and pregnancy-based survey (part of the European Studies on Infertility and Subfecundity), we obtained information on the number of offspring, adverse pregnancy outcomes, age at pregnancy, and waiting time to pregnancy. The German portion of these surveys also included information on physician-diagnosis of asthma, atopic eczema, or hay fever. The odds ratio (OR) adjusted for age showed that the number of children was reduced among women with atopy (OR = 0.75, 95% CI: 0.57-0.98 in the pregnancy-based sample; OR = 0.79, 95% CI: 0.63-0.99 in the population-based sample). We did not identify other signs of reduced reproductive ability in atopic women. The results provide support for two assumptions: (i) either a lower number of offspring in atopic mothers combined with an increased risk of atopy in offspring of atopic mothers may explain the protective effect of a higher number of siblings on atopy in offspring; or (ii) successive pregnancies may decrease the atopic response of the mother and thus the risk of developing atopy in subsequent offspring.