Factors associated with size and proportionality at birth in term Jamaican infants.

The objective of this study was to identify the factors associated with size and proportionality at birth in a cohort of term infants established to investigate their growth and development. One hundred and forty term low-birth-weight (birth-weight < 2,500 g) infants and 94 normal birth-weight infants (2,500- < 4,000 g) were recruited within 48 hours of birth at the main maternity hospital, Kingston, Jamaica. Birth anthropometry and gestational age were measured, and maternal information was obtained by interview and from hospital records. Controlling for gestational age, variables independently associated with birth-weight were rate of weight gain in the second half of pregnancy, maternal height, haemoglobin level < 9.5 microg/dL, time of first attendance in antenatal clinic, birth order, pre-eclampsia, and consumption of alcohol, with 33% of the variance in birth-weight explained. Birth length was associated only with maternal height and age, while measures of proportionality (ponderal index and head/length ratio) were associated with characteristics of the environment in late pregnancy, including rate of weight gain, weight in late pregnancy, and pre-eclampsia. The variation in maternal characteristics associated with size or proportionality at birth may reflect the times during gestation when different aspects of growth are most affected.