Effects of intrauterine position on the behavior and genital morphology of litter-bearing rodents

We review the literature describing hormonally mediated effects of intrauterine position on the genital morphology and reproductive behaviors of litter-bearing rodents. We emphasize work carried out in our own laboratory in which male and female Mongolian gerbils served as subjects. The results of the studies we consider indicate that biologically significant aspects of the variance in morphology and reproductive strategy seen in all populations of adult rodents reflect variance in perinatal levels of exposure to gonadal hormones induced by intrauterine position. We conclude that studies of correlations between intrauterine position and adult characteristics provide opportunities to examine the impact of normal variation in perinatal exposure to hormones on adult mammalian phenotypes.