Association between preterm birth and maternal allergy considering IgE level

The aim of this study was to explore the association between maternal allergies and preterm birth by different total immunoglobulin E (IgE) levels. Data of 81 791 pregnant women from the Japan Environment and Children's Study, a prospective birth cohort, were used. Maternal allergic diseases, including a history of bronchial asthma (BA), atopic dermatitis (AD), and allergic rhinitis (AR), were obtained by self-administered questionnaires. Total serum IgE levels were measured at the first trimester and obstetrical outcomes from medical records transcripts were analyzed. The association between maternal allergic disease and obstetric outcome, including threatened abortion, preterm labor, early preterm birth (22-33 weeks), and late preterm birth (34-36 weeks), were examined by logistic regression. Subgroup analyses were performed by IgE level. Maternal BA and AR were associated with an increased risk of threatened abortion and preterm labor, but high total IgE level was associated with a decreased risk of preterm labor. There was little difference in associations between allergic disease and threatened abortion and preterm labor by total IgE levels. Although there was no significant association between allergic disease and preterm birth, if total IgE was high, AR was significantly associated with a decreased risk of early preterm birth (adjusted odds ratio, 0.60; 95% confidence interval 0.43-0.86). There was significant evidence for differences associated with total IgE levels (P-values for the interaction of the effects of AD and AR on early preterm birth were 0.039 and 0.015, respectively). The effect of allergy on preterm birth might differ depending on the total IgE level.