New York City birth certificates for singletons born from September 1-December 31, 1981 (N = 36,056) were analyzed using multivariate regression techniques. The effects of maternal age and parity on birthweight were assessed. There was a significant progression of birthweight with advancing age. Birthweight similarly increased from parity 1 to parity 3, but dropped markedly in the higher parity groups. On stratification by gestational age, we found that age and parity influence birthweight by affecting fetal growth rather than the length of pregnancy.
PIP: New York City birth certificates for singletons born from September 1-December 31, 1981 (N=36,056) were analyzed using multivariate regression techniques. The effects of maternal age and parity on birthweight were assessed. There was a significant progression of birthweight with advancing age. Birthweight similarly increased from parity 1 to parity 3, but dropped markedly in the higher parity groups. On stratification by gestational age, it was found that age and parity influence birthweight by affecting fetal growth rather than the length of pregnancy. A number of theories are offered as possible explanations for the increased occurence of growth retardation in infants of mothers of distinct age and parity groups. Many investigators report that with teenage mothers, this can be attributed to the demands of the growing fetus being superimposed on the nutritional needs of the teenagers, who are often themselves still in the growth stage. It has been reported that maternal nutrition may change over different parities, with both vitamin B1 and chromium, a trace metal with a possible role in carbohydrate metabolism, found to be lower in grand multiparous women. The inadequate concentrations of nutrients flowing from the placentae of these groups of women decrease the nourishment to the fetus, resulting in the birth of infants with decreased birthweights who are born at normal gestational ages. However, these findings cannot be confirmed until biological research, particularly on the question of maternal nutrition and metabolism, is carried out.