Previous Reproductive History and the Susceptibility to X-ray-induced Congenital Anomalies

Abstract

THE suspicion that primiparous mice are more apt to produce anomalous offspring, following foetal X-irradiation, than are multiparous mice, has led to the necessity of determining the normal incidence of such anomalies among large numbers of control mice of both categories. This investigation deals with the normal primiparous and multiparous CF1 mice of exactly the same age (7–9 months) and the analysis of the condition of their offspring. In direct contrast with this is presented a parallel study of pregnant primiparous and multiparous CF1 mice X-irradiated at a specific time and to a specific dose to determine whether a single variable (primiparity or multiparity) might alter the incidence of anomalies induced by X-rays. This paper reports data from 225 litters (2,700 implantations).