RESUMEN
BACKGROUND: It is not yet known whether the risk of developing atopic dermatitis (AD) is influenced by preterm birth. Moreover, AD risk has not been assessed in a large sample of extremely preterm infants (< 29 weeks' gestation). OBJECTIVES: To determine whether the risk of AD is influenced by preterm birth. METHODS: We investigated the relationship between gestational age (GA) and AD using data from two independent population-based cohorts, including a total of 2329 preterm infants, of whom 479 were born extremely preterm. RESULTS: There was a lower percentage of children with AD in the extremely preterm group compared with those born at a greater GA (Epipage cohort, 2-year outcome: 13·3% for 24-28 weeks, 17·6% for 29-32 weeks, 21·8% for 33-34 weeks, P = 0·02; LIFT cohort, 5-year outcome: 11% for 24-28 weeks, 21·5% for 29-32 weeks, 19·6% for 33-34 weeks, P = 0·11). After adjusting for confounding variables, a lower GA (< 29 weeks) was significantly associated with decreased risk of AD in the Epipage cohort [adjusted odds ratio (aOR) 0·57, 95% confidence interval (CI) 0·37-0·87; P = 0·009] and the LIFT cohort (aOR 0·41, 95% CI 0·18-0·90; P = 0·03). CONCLUSIONS: Very low GA (< 29 weeks) was associated with a lower risk of AD compared with higher GA (29-34 weeks) and full-term birth.