First- and second-trimester fetal size and asthma outcomes at age 10 years.

Rationale: Greater early fetal size is associated with reduced asthma risk and improved lung function in early childhood.

Objectives: To test the hypothesis that associations between early fetal size, asthma symptoms, and lung function persist into later childhood.

Methods: In a longitudinal study, first- and second-trimester fetal measurements were recorded. At 10 years of age a respiratory questionnaire was completed. Spirometry, bronchial challenge, and skin-prick testing were undertaken in a subset.

Measurements And Main Results: Fetal measurements were available in the first trimester for 853 individuals and the second trimester for 1,453. Questionnaires were returned for 927 children and 449 underwent detailed phenotyping. For each millimeter increase in first trimester size, asthma risk reduced by 6% (95% confidence interval[CI], 1–11) and FEV1 was higher by an average of 6 ml (95% CI, 1–11).First-trimester size was reduced in those with asthma at both 5 and 10 years compared with early or late onset wheeze (P , 0.02). Compared with persistent high growth in first and second trimesters,persistent low growth was associated with increased asthma risk(odds ratio, 2.8; 95% CI, 1.2–6.9) and a mean reduction in FEV1 of 103 ml (95% CI, 13–194), whereas increasing fetal size was associated with increased eczema risk (odds ratio, 2.5; 95% CI, 1.2–5.3).

Conclusions: Reduced fetal size from the first trimester is associated with increased risk for asthma and obstructed lung function in childhood. Relative change in size after the first trimester is associated with eczema.