Possible effects of x-ray exposure during fetal life on the subsequent reproductive performance of human females

This continuing study investigates possible effects of x-ray exposure during fetal life on the later fertility of human females and on their offspring. The study population comprises 1458 black females exposed to x-ray during fetal life, each with an unexposed control matched by hospital of birth, parity, and birth date; all were born in 1947-1952 and are residents of Baltimore City. At the end of 1970 these in utero exposed and unexposed control females had a total of 2422 live births and fetal deaths ascertained from Baltimore City vital records. Exposed women had significantly more live and still births than controls. The observed level of increased fertility in exposed subjects is 10 to 15%. The possible confounding influence of economic, social, and medical differences between exposed and control members of the study population has been stringently analyzed by several methods, and the fertility difference remains. The possibility that the observed increase in fertility among exposed women may be related to their in utero exposure is supported by several studies in experimental animals that show temporary increases in fertility early in reproductive life after preconception, prenatal or juvenile exposure to low doses of radiation. Analysis of fetal and infant mortality among the offspring of study population members showed a nonsignificant excess in the exposed group. Causes of death that were increased if the mother was exposed were congenital anomalies (ICD 746-759) and conditions of membranes, placenta, and cord (ICD 769-771).