WEIGHT IN RELATION TO FETAL AND NEWBORN MORTALITY; INFLUENCE OF SEX AND COLOR

Abstract

Analysis was made of 209,055 live births, 6978 fetal deaths subsequent to 20 weeks of gestation, and 5048 neonatal deaths, reported in New York City in 1939 and 1940. Comparison was made of fetal death rates per 1000 unborn children in each weight group by means of a modified life table method and of neonatal death rates per 1000 live births in each birth-weight group, for the two sexes and for the white and nonwhite races. For all infants, fetal death rates, so calculated, are relatively low and neonatal death rates very high in the lower weight groups. Both rates go up sharply in the higher weight groups, indicating that infants much over average weight are not good risks. Lower fetal death rates were observed for females in the weight groups below 3000 gm. and for males in the weight groups above 3000 gm. Neonatal death rates were lower for females throughout. The implication appears to be that relative maturity is more important than size in regard to variation in fetal death rate. Comparison by race indicates consistently higher nonwhite fetal death rates for nonwhite infants in all weight groups. Neonatal death rates were similar for white and nonwhite infants in the lower weight groups but higher for nonwhite infants in the upper weight groups. A study in 22 hospitals, giving presumably better care than the city-wide average, showed lower neonatal rates for the nonwhite infants in the lower weight groups. It is inferred that comparisons of observed mortality differences by race must consider differences between the races in regard to extrinsic factors such as economic status, nutrition and care. For practical purposes a uniform criterion of birth weight, 2500 gm., should be maintained in the diagnosis of prematurity. Using a method of combining fetal and neonatal mortality experience to measure the total risk to unborn children of different weights, it was possible to calculate "best birth weights." These were found to be about 120 gm. lower for female than for male, and about 160 gm. lower for nonwhite than for white births.