Abstract

Fetal weight data from 84 litters of Sprague-Dawley rats were statistically analyzed for the effect of position in the uterine horn on fetal weight. The standard score obtained from the mean weight and standard deviation of all fetuses in a uterine horn were studied for position effect. In control group, the heaviest fetus occupied the middle position with a progressive decrease in weights toward the ovarian and cervical ends of the horn. But the effect related to position for the fetal weight was not statistically significant. In contrast, rats acutely or chronically exposed to carbon monoxide showed statistically significant positional differences of fetal weight within the uterine horns. The findings that the intrauterine position effect on fetal weight which is not significant in control group may act one of confounders at the situation of transplacental toxicological studies.