Effects of maternal stress on puberty, fertility and aggressive behavior of female mice from different intrauterine positions.

We examined the effects of maternal stress (bright light and heat) during the last third of pregnancy on subsequent reproductive and behavioral characteristics of female mice from different intrauterine positions. Female mice that develop in utero between two male fetuses (2M females) differ from females that develop between two female fetuses (0M females) in their serum concentrations of both testosterone and estradiol during the fetal period of sexual differentiation. After birth, 0M and 2M females differ in a wide range of reproductive characteristics. We examined the effects of maternal stress on the response to social cues regulating the timing of first vaginal estrus and the length of the first postpubertal estrous cycle when 4 0M or 4 2M females were housed together next to an adult male. Maternal stress decreased the inhibitory effect of being housed with other females in terms of the length of the first postpubertal estrous cycle, but this only occurred in 0M females. We found no effect of maternal stress or intrauterine position on the capacity to mate and remain pregnant, regardless of whether 0M or 2M females were stressed or not stressed during early pregnancy prior to implantation. While there was no effect of prior intrauterine position on interfemale aggression or behavior toward young, maternal stress did tend to reduce the likelihood that females (in diestrus) would exhibit aggression toward other females.