Maternal preeclampsia and childhood asthma in the offspring

BackgroundPreeclampsia is a possible risk factor for childhood asthma in the offspring. Our aim was to find whether preeclampsia is associated with childhood asthma. We also aimed to study whether a possible association can be explained by factors shared by siblings. MethodsAll eligible live singletons born in Denmark during 1993-2007 were identified (N=923,533), and the occurrence of preeclampsia during the index pregnancy was determined. The children were followed from their 3rd birthday to the first hospitalization, outpatient contact or prescription for asthma, emigration, death, their 18th birthday, or the end of 2010, whichever came first. We carried out a nested case-control and a case-sibling study with density sampling to estimate incidence rate ratio (IRR) of asthma as a function of maternal preeclampsia, using conditional logistic regression. ResultsA total of 115,522 asthma cases were identified during 1996-2010. In the case-control analysis, the overall IRR of asthma for those exposed to maternal preeclampsia was 1.19 (95% confidence interval (CI): 1.15, 1.24). The IRRs for asthma according to early and late onset preeclampsia were 1.88 (95% CI: 1.67, 2.11) and 1.14 (95% CI: 1.10, 1.19). In the case-sibling analysis, the corresponding IRRs were 1.06 (95% CI: 0.98, 1.14), 1.15 (95% CI: 1.02, 1.29), and 1.02 (95% CI: 0.93, 1.11), respectively. ConclusionsEarly onset preeclampsia was associated with an increased risk of asthma in the offspring, but part of this association may be due to confounding by factors shared by siblings.