COMPARISON OF BIRTH-WEIGHT DISTRIBUTIONS BETWEEN CHINESE AND CAUCASIAN INFANTS

To assess the reasons for the Chinese-Caucasian differences in birth w eight distributions, a cohort study was carried out involving 18,665 C aucasian and 1,597 immigrant Chinese infants born at Montreall's Royal Victoria Hospital from January 1978 to March 1990 and 1,862 native Ch inese infants born at Hefei Maternal and Infant Hospital in Hefei, Peo ple's Republic of China, from September 1990 to August 1991. Mean (sta ndard deviation) birth weights in grams were 3,369 (567), 3,195 (493), and 3,171 (428) (p < 0.01 for differences in mean and variance), and mean (standard deviation) fetal growth ratios (ratio of observed birth weight to average birth weight at the same gestational age) were 0.99 4 (0.124), 0.963 (0.114), and 0.935 (0.112) (p < 0.01 for differences in mean and variance), respectively, in the Caucasian, immigrant Chine se, and native Chinese groups. No important or consistent Chinese-Cauc asian differences in gestational age were found, When mothers with ext reme values for demographic, anthropometric, nutritional, and lifestyl e determinants of fetal growth were excluded, the mean fetal growth ra tio in Caucasian infants remained significantly higher (p < 0.01), but the standard deviations became more similar (p > 0.05): Mean (standar d deviation) fetal growth ratios were 1.001 (0.111), 0.966 (0.108), an d 0.946 (0.114), respectively. The race-specific rate of growth differ ed according to period of gestation, with Chinese infants showing more rapid fetal growth early in the third trimester but slower growth nea r and after term. The authors conclude that the lower mean birth weigh t in Chinese infants is due to differences in fetal growth (rather tha n gestational duration) and by their inherently slower growth at or af ter term. The tight distribution of birth weight among the Chinese is caused partly by their reduced exposure to extremes of maternal determ inants of fetal growth (mediated largely by environmental mechanisms) and partly by their inherently different growth pattern, with faster g rowth at earlier gestations but slower growth at later gestations.