STUDIES ON THE MAINTENANCE OF PREGNANCY IN THE WHITE EAT11

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Abstract
A study of the effect of ovariectomy on pregnant rats indicates that pregnancy may continue for much longer periods following ovariectomy than the 48 hrs. generally reported. The avg. duration of pregnancy following bilateral ovariectomy of 46 animals was 80 hrs. One animal carried a living fetus at autopsy, 162 hrs. after ovariectomy. The duration of pregnancy following ovariectomy was prolonged by the use of operative techniques, such as 2-stage ovariectomy, which reduced the amt. of operative shock. Best results were obtained by combining a 2-stage procedure with the technique of pulling the ovaries out between the skin and the body-wall musculature where they could be reached later with a minimum of delay and trauma. Using these methods the avg. duration of pregnancy in 1 series was greater than 108 hrs. This was 28 hrs. longer than in the control series. Pregnancy continued for more than 187 hrs. in one case. Although it was impossible to determine the extent of the role of shock by its complete elimination, it was concluded that trauma was a definite factor in hastening abortion. It was thought that the use of ovarian ear grafts would provide a way of removing the ovarian hormone source with an absolute minimum of trauma. However, in the limited amt. of work done, no success in maintaining pregnancy with ovarian ear grafts was attained. Effects of small amts. of estrone, progesterone, and combinations of these on duration of pregnancy following ovariectomy were tested and the results compared with extensive control data from previous work. No definite maintenance effects were noted until quantities of 2.0 mg. of crystalline progesterone at the time of castration and 10.0 I.U./day of estrone were given. The increased duration of pregnancy found in these expts. was not due to an excess of placentae which might result in a high placenta: fetus ratio. Embryos were prob- ably killed by pressure of the uterine wall following removal of the ovaries in some instances,.

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