Rationale Asthma in pregnancy is associated with respiratory diseases in the offspring.
Objective To investigate if maternal asthma is associated with lung function in early life.
Methods Data on lung function measured at 5–6 weeks of age were combined from two large birth cohorts: the Bern Infant Lung Development (BILD) and the Australian Breathing for Life Trial (BLT) birth cohorts conducted at three study sites (Bern, Switzerland; Newcastle and Sydney, Australia). The main outcome variable was time to reach peak tidal expiratory flow as a percentage of total expiratory time(tPTEF:tE%). Bayesian linear hierarchical regression analyses controlling for study site as random effect were performed to estimate the effect of maternal asthma on the main outcome, adjusting for sex, birth order, breast feeding, weight gain and gestational age. In separate adjusted Bayesian models an interaction between maternal asthma and sex was investigated by including an interaction term.
Measurements and main results All 406 BLT infants were born to mothers with asthma in pregnancy, while 193 of the 213 (91%) BILD infants were born to mothers without asthma. A significant interaction between maternal asthma and male sex was negatively associated with tPTEF:tE% (intercept 37.5; estimate: –3.5; 95% credible interval –6.8 to –0.1). Comparing the model posterior probabilities provided decisive evidence in favour of an interaction between maternal asthma and male sex (Bayes factor 33.5).
Conclusions Maternal asthma is associated with lower lung function in male babies, which may have lifelong implications on their lung function trajectories and future risk of wheezing and asthma.
- paediatric lung disease
- respiratory measurement
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Contributors JM, UF, PL, PDR and AMC conceived the project and supervised the lung function analysis. PGG, VEM and JM conducted the Breathing for Life Trial (BLT) pregnancy study. JM, PGG, VEM, AMC, PDR, PDS and KH conducted the BLT infant follow-up. PDGB, KJ and EDQA performed the infant lung function. JM supervised the BLT infant follow-up. UF and PL supervised the Bern Infant Lung Development (BILD) study follow-up. UF, PL, RA, OG, OF and JU conducted the BILD infant follow-up. CO and GMCG performed the multivariable Bayesian regression analyses. CO supervised all other statistical analyses and wrote the statistical method section. PDGB and EDQA analysed all lung function data. PDGB and JM wrote a draft manuscript. All authors edited the final version of the manuscript.
Funding The study was funded by the National Health and Medical Research Council, Hunter Children’s Research Foundation; Hunter Medical Research Institute, PRC GrowUpWell University of Newcastle; and Charitable Trust, John Hunter Hospital.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The BLT study was approved by the Hunter New England Human Research Ethics Committee of the Hunter New England Local Health District (ref no 12/10/17/3.04). The BILD study was approved by The Bernese Cantonal Ethics Research Committee (Bern, Switzerland).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request.
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