Asthma, Atopic Dermatitis Risk May Be Affected by Timing of Birth

Compared with full-term birth, early-term birth was associated with an increased risk for asthma by 7 years of age and post-term birth and emergency Caesarean delivery (CD) were associated with increased risk for atopic dermatitis, according to the results of a Finnish study published in Pediatric Pulmonology.

Paivi Korhonen, MD, PhD, from the Department of Pediatrics, Tampere University Hospital, Finland, and colleagues assessed the incidence and risk factors for asthma and atopic dermatitis by 7 years of age after early-term (37-38 weeks), full-term (39-40 weeks), late-term ( 41 weeks), and post-term (≥42 weeks) birth in 965,203 infants born between 1991 and 2008 in Finland. They analyzed data from national health databases on asthma medication reimbursement and hospital visits for atopic dermatitis.

The frequencies of asthma medication reimbursement were 4.5%, 3.7%, 3.3%, and 3.2% in the early-term, full-term, late-term, and post-term groups, respectively (P <.001). Population-attribute risk (PAR) analyses found that the most relevant risk factors for asthma were male sex, hospital visits resulting from atopic dermatitis (as a surrogate for atopic tendency), tobacco smoke exposure during pregnancy, early-term birth, and birth by elective CD. Maternal age of 40 years or older and being first-born or born in a level II hospital were associated with a decreased risk for asthma.

Hospital visits for atopic dermatitis were most common after post-term birth (odds ratio, 1.10). PAR analyses found that male sex, first delivery, birth in a level II hospital, and birth by emergency CD were the most relevant risk factors for atopic dermatitis. In contrast, smoking during pregnancy and place of birth other than a level III or level II hospital appeared to decrease the risk.

The researchers noted that differences in recording practices in different hospitals and regions are a common limitation in register studies; however, they maintained that the Finnish health information system is based on national registers of high quality, with good coverage. Nonetheless, no data were obtained on ethnic background, parental asthma or atopy, indications for CD, psychosocial factors, breastfeeding, or environmental conditions. Furthermore, reliable data on socioeconomic status were also missing. Atopic dermatitis was identified using hospital visits only, which indicates severe disease. As a consequence, cases of milder disease may have been missed.

The authors concluded that the findings indicate a need for counseling against smoking during pregnancy and strict indications for elective CD to reduce the risk for asthma in children, whereas the findings on post-term birth and atopic dermatitis demonstrate the importance of optimal timing of delivery after due date.

Reference

Korhonen P, Haataja P, Ojala R, et al. Asthma and atopic dermatitis after early-late-and post-term birth [published January 5, 2018]. Pediatr Pulmonol. doi:10.1002/ppul.23942