Fetal and postnatal growth and body composition at 6 months of age.

Objectives: The objectives of the study was to examine which parental, fetal, and postnatal characteristics are associated with fat and lean mass at the age of 6 months and examine the effect of growth (catch-down, catch-up) in fetal life and early infancy on fat and lean mass.

Design: This study was embedded in the Generation R Study, a prospective cohort study from early fetal life onward. Body composition was measured by dual-energy X-ray absorptiometry in 252 infants at 6 months. Parental, fetal, and postnatal data were collected by physical and fetal ultrasound examinations and questionnaires.

Results: Children with fetal catch-up in weight (gain in weight sd score >0.67) in the second trimester tended to have a higher fat mass percentage [FM(%)] at 6 months of age, whereas children with fetal catch-down in weight had a lower FM(%) compared with nonchangers. In the third trimester, both catch-up and catch-down in weight were associated with an increase in FM(%) at 6 months. Children with catch-down in the third trimester had a greater risk for postnatal catch-up in weight greater than 0.67 sd score. Birth weight and weight at 6 wk were positively associated with fat mass at 6 months. Postnatal catch-up in weight within 6 wk after birth had the highest association with total and truncal FM(%) at 6 months. Total and truncal FM were higher in girls.

Conclusion: Catch-down in weight in the third trimester was strongly associated with postnatal catch-up within 6 wk after birth, and both were associated with an increase in fat mass at the age of 6 months. Our study shows that fetal as well as postnatal growth patterns are associated with body composition in early childhood.