Maternal asthma, premature birth, and the risk of respiratory morbidity in schoolchildren in Merseyside.
BACKGROUND--A study was carried out to analyse the impact of maternal asthma on the risk of preterm delivery and the contribution of preterm delivery to the development of childhood asthma. METHODS--Two cross sectional community studies of 1872 children (5-11 years) in 1991 and 3746 children in 1993 were performed. A respiratory health questionnaire was distributed throughout 15 schools in Merseyside and completed by the parents of the children. RESULTS--Asthmatic mothers were more likely to have a preterm delivery than non-asthmatic mothers (odds ratio (OR) 1.49; 95% CI 1.10 to 2.02). Smoking was a separate risk factor for preterm delivery (OR 1.35; 95% CI 1.10 to 1.65). Asthmatic mothers did not have an increased risk of delivering small, growth retarded babies. Maternal asthma, paternal asthma, and premature birth, in that order, increased the risk of later childhood respiratory morbidity (OR 3.13, 95% CI 2.36 to 4.16; 2.23, 95% CI 1.62 to 3.05; 1.40, 95% CI 1.10 to 1.79). Conversely, babies who were small for gestational age appeared less likely to develop doctor diagnosed asthma or the symptom triad of cough, wheeze, and breathlessness in childhood, although this was not statistically significant (OR 0.63, 95% CI 0.28 to 1.41). CONCLUSIONS--Maternal smoking during pregnancy and maternal asthma are independent risk factors associated with preterm delivery. Asthma in mothers predisposes to preterm delivery but not fetal growth retardation. Preterm birth, but not growth retardation, predisposes the child to the development of subsequent asthma.