CHILD DEVELOPMENT I: BEHAVIORAL SCIENCE AND EPIDMIOLOGY: Perinatal mortality, economic and racial influences on the sex ratio

Abstract

An excess of fetal and neonatal deaths in male offspring is found in man, domestic animals and some insects. In humans, the male disadvantage is reportedly less when perinatal infant mortality is high, i.e. in nonwhites and the socioeconomically disadvantaged. The present study offers some explanations. In an analysis of 2735 consecutive newborn autopsies, the ratio of males to females was 1.28:1 which differs significantly from the 1.05:1 ratio for all U.S. live-births. Within this series the ratio for stillbirths was 0.95:1 and for live-births 1.45:1. Most disorders which were present in both stillborn and liveborn infants had a much lower male:female ratio in the former group. The ratio for infants of poor families was 1.17:1, nonpoor 1.40:1, whites 1.34:1, blacks 1.22:1, Puerto Ricans 1.22:1, and Mexican-Americans 1.23:1. The ratio for liveborns with infections of antenatal origin was 1.15:1 whereas the ratio for infants with infections acquired after birth was 1.58:1. Removal of the cases with antenatal infections from the analysis eliminated much of the sex ratio difference between whites and nonwhites and between the poor and the nonpoor. A decreasing incidence of such antenatal infections may well explain why the ratio of male to female neonatal deaths is increasing in the U.S. and other industrial societies and why U.S. poor whites and nonwhites have fewer excess male deaths than their more prosperous counterparts.