Maternal blood pressure throughout pregnancy, gestational hypertension, and preeclampsia and offspring asthma

Background: The association between hypertensive disorders during pregnancy and offspring asthma remains unclear, but preeclampsia appears to be an independent risk factor. Objectives: To investigate the associations of maternal blood pressure at multiple time-points during pregnancy, gestational hypertension, and preeclampsia with risk of offspring asthma between 10 and 32 years of age. Methods: We performed a cohort analysis of a randomized controlled trial of iron supplementation conducted in 1985-86 in Finland. Of 2,694 pregnant women recruited, 2,666 pregnancies ended in a live birth. Maternal systolic and diastolic blood pressure was taken at 12, 20, 28, and 36 weeks gestation. Gestational hypertension and preeclampsia were defined according to criteria of the International Society for the Study of Hypertension in Pregnancy. Trial data were linked to register for reimbursement of asthma medications to ascertain offspring asthma. Adjusted risk ratios (RRs) for potential confounding factors were estimated. Results: The prevalence of gestational hypertension and preeclampsia was 12% and 3%, respectively. Asthma was present in 3% of offspring. We found no associations between blood pressure measurements at any time-point of pregnancy and offspring asthma. However, gestational hypertension was associated with a reduced risk (RR 0.24, 95% CI 0.06-0.97), while preeclampsia was associated with an increased risk (RR 3.09, 95% CI 1.45-6.54) of offspring asthma. Conclusions: Maternal prenatal blood pressure was not associated with offspring asthma. However, gestational hypertension was associated with reduced risk, while preeclampsia was associated with increased risk.