The Effect of Maternal Age, Parity, Fetal Sex and Season upon Early Intrauterine Development

Abstract

This report presents the results of a computer analysis of 1672 specimens of embryonic material which were obtained by induced abortion in normal pregnancies. The study was undertaken to evaluate the effect of maternal age, parity, fetal sex and seasonal variations on the growth rate of embryos and fetuses which were between six and 20 weeks' gestation. Two parameters of intrauterine growth were analyzed: (a) the relation between menstrual age and crown‐to‐rump length and (b) the crown‐to‐rump length versus the body weight ratio. None of the quoted factors seemed to affect the linear growth of the embryo or fetus. The correlations between fetal crown‐to‐rump length and body weight were not influenced by maternal age, parity or fetal sex. Significant (p < 0.001) differences in early intrauterine growth rates were detected in relation to the season of conception. The rate of increase of body weight was far above average in those embryos and fetuses conceived during the summer months, while the opposite was the case when the conception occurred in the fall. An increase in the rate of the weight gain was demonstrated among the products of conceptions which occurred in the winter. There were insufficient data about those fetuses that resulted from conceptions which occurred in the spring.