The association of maternal growth and socio-economic measures with infant birthweight in four ethnic groups.

BACKGROUND Both maternal socio-economic status (SES) and growth measures are themselves interrelated and are also related to infant birthweight. The objective of this study is to compare the relative importance of such maternal measures as determinants of birthweight of female infants-the prospective mothers of the next generation. METHODS The study base was derived from a population-based multiethnic intergenerational cohort: the Washington State Intergenerational Cohort. Infants of mothers from four ethnic groups were included: non-Hispanic Whites, African Americans, Native Americans, and Hispanics. We generated simple, partial, and multiple correlation coefficients to investigate the association between birthweight and the maternal growth and SES measures. RESULTS While there were slight differences among the ethnic groups, generally each of three maternal pre-conceptional growth measures-birthweight, stature, and pre-pregnant weight-was a stronger predictor of female infant birthweight than were each of the five maternal SES factors-age, parity, marital status, educational attainment, and prenatal care onset. After accounting for the proportion of variation in birthweight explained by the maternal growth measures and maternal smoking, the addition of the five SES variables added relatively little to the prediction of infant birthweight. The maximal multiple correlation coefficients (R2) yield values ranging from 9.5% to 12.8%. CONCLUSIONS A mother's growth before pregnancy is a stronger predictor of infant birthweight than is her current socio-economic circumstance. Since the mother's growth must have been influenced by the socio-economic circumstances of her family of upbringing, this further highlights the intergenerational contribution on a woman's reproductive success.