Associations of preterm births with child health and development: Japanese population-based study

Objective To examine associations between the duration of gestation and health and development outcomes at 2.5 years and 5.5 years using a Japanese population-based longitudinal survey (n = 47â€̂015). Study design Hospitalization was used as an indicator of physical health, and responses to questions about age-appropriate behaviors were used as an indicator of behavioral development. We conducted logistic regression analyses controlling for a set of neonatal and family factors. We also estimated population-attributable fractions. Results We observed a steady increase toward shorter duration of gestation in the risk of hospitalizations at age 2.5 years and 5.5 years and developmental delays at 2.5 years (P_{linear trend} <.001 for all outcomes). We found associations only between extremely preterm birth and delayed behavioral development at age 5.5 years. Conclusion There is a linear relationship between shorter duration of gestation and increased risk of later health and developmental problems. In line with Rose's "population paradox," the population-attributable risks for these problems are greater for moderately preterm infants compared with extremely preterm infants.