Reproductive history and allergic rhinitis among 31145 Danish women

BACKGROUND AND OBJECTIVE: A successful pregnancy is associated with a strong skewing of the immune system towards a Th2-type immune response. Because such a deviation is also the hallmark of allergic disease, it was investigated whether allergic rhinitis in women was associated with an increased likelihood of becoming pregnant and having a successful outcome of pregnancies. MATERIAL AND METHODS: Information on allergic rhinitis and reproductive history was obtained for 31145 pregnant women who participated in a national birth cohort study in Denmark during September 1997 to March 2000, and for whom complete information on siblings and place of residence and birth was available via the Civil Registration System. Data were analysed using logistic regression. RESULTS: Women who had previously been pregnant (OR = 0.91, 95% CI 0.85-0.98) or who had given birth previously (OR = 0.91, 95% CI 0.85-0.98) were less likely to report allergic rhinitis than others. The number of previous spontaneous abortions, gestational week of the first spontaneous abortion and fertility treatment were not associated with allergic rhinitis. Women who had waited less than a year to become pregnant more often had allergic rhinitis (OR = 1.18, 95% CI 1.06-1.32, P = 0.002) than women who had waited for more than a year. Early age at menarche was associated with an increased likelihood of allergic rhinitis (Ptrend = 0.003). CONCLUSIONS: Our findings did not support the hypothesis that an atopic genotype overall should be associated with an increased likelihood of successful outcome of pregnancies, but it might be associated with a decreased waiting time to pregnancy.