PLASMA TESTOSTERONE IN FETAL RATS AND THEIR MOTHERS ON DAY-19 OF GESTATION

Plasma testosterone levels were higher in pooled samples from male fet uses than from female fetuses on day 19 of pregnancy. Plasma testoster one from female fetuses with males located caudally in the uterus was higher than from females that lacked such males. Testosterone level of both male and female fetuses was correlated with maternal testosteron e. No correlation was found between maternal testosterone and number o f males in the litter, male-to-female ratio, or litter size. These res ults corroborate earlier findings of a sex difference in plasma testos terone levels on fetal day 19 in rats, and provide support for the hyp othesis that female rats receive androgens from males located caudally in the uterus. No evidence was found that testosterone of pregnant fe males is affected by the sex ratio or size of her litter.