Longitudinal Changes in Lung Function during Pregnancy: The Impact of Asthma

Abstract

Background: Pregnancy produces physiological effects on the respiratory system; the interplay of gestation and maternal asthma remains poorly characterized. Characterizing longitudinal lung function in pregnant women with and without asthma provides a potential opportunity to examine respiratory adaptations and risks during pregnancy. Objective: To investigate the effect of advancing gestation, and its interaction with asthma, on lung function of pregnant women. Methodology: This prospective longitudinal cohort study took place in Multan, Pakistan, and recruited 460 pregnant women (230 with asthma and 230 as non-asthmatic controls). Women were recruited at 12–22 weeks of gestation and followed until the third trimester. Spirometry was undertaken at three standardized time points to evaluate forced vital capacity (FVC%), forced expiratory volume in 1 second (FEV1%), and FEV1/FVC ratio according to ATS/ERS guidelines. Results: At baseline, the asthmatic women demonstrated significantly lower FEV1% compared to their non-asthmatic counterparts (88.9 ± 9.3 vs. 94.8 ± 8.7). On average, FVC% decreased through gestation in both groups, but it decreased to a greater degree in the history of asthma group (−0.12% per week, 95% CI −0.16 to −0.08) compared to the asthmatic group (−0.07% per week, 95% CI −0.11 to −0.03). FEV1% declined significantly for non-asthmatic women but remained unchanged for the asthmatic women during pregnancy. Conclusion: Pregnancy has differential effects on lung function when examining asthma status. Non-asthmatic women have relatively greater restrictive changes, while asthmatic women see stable expiratory function and can expect a modest improvement in FEV1/FVC ratio.