Growth and development of term children born with low birth weight: Effects of genetic and environmental factors

Objective: To evaluate the role of intrauterine growth retardation (IUGR) on childhood growth and development, controlling for environmental and genetic factors. Methods: Women and infants enrolled in the National Collaborative Perinatal Project were analyzed. Weight, length, and IQ were assessed at birth and at 7 years in the entire National Collaborative Perinatal Project population in term infants born with and without IUGR ("population cohort"). To control for genetic and environmental factors, growth and development were also compared in 220 similar-sex term sibling pairs in which one sibling was born with IUGR and one was born without IUGR ("sibling cohort"). Results: At 7 years of age heights and weights of infants born with IUGR remained similar to 0.5 SD less than infants born without IUGR (weight-for-age: p < 0.001, height-for-age: p < 0.001). In the entire National Collaborative Perinatal Project population, IQ (p < 0.001) and Bender-Gestalt (p < 0.001) scores were significantly lower in infants born with IUGR compared with those in infants born without IUGR. There were no significant differences in IQ or Bender-Gestalt scores between siblings born with and without IUGR. However, siblings with IUGR and large deficits in head circumference demonstrated both decreased IQ (p < 0.05) and Bender-Gestalt (p < 0.05) scores. Conclusion: Long-term growth deficits associated with IUGR appear largely independent of prenatal or postnatal environmental factors. IUGR had little impact on intelligence and motor development except when associated with large deficits in head circumference.