Casual observations of pregnant females injected with testosterone propionate (T.P.) suggested that they do not display masculine behavior until after parturition nor do they have clitoral hypertrophy although their female offspring are strongly masculinized (Endocrinology, 65: 369, 1959).
Systematic tests of such animals and of suitable controls have recently been completed. The groups tested were composed of pregnant animals injected with T.P. during gestation, pregnant animals which were not injected, and injected and uninjected nonpregnant animals. The injection periods (47 days) in the pregnant and nonpregnant animals were identical.
The results reveal that the pregnant guinea pigs receiving T.P. mounted a group mean of 0.3 times per test whereas the uninjected pregnant controls and the nonpregnant controls had group means of 0.2 and 0.3 mounts, respectively. The differences were not significant. The injected pregnant animals did not show much clitoral modification. Injected nonpregnant females, however, were masculinized behaviorally, as revealed by a group mean of 7.7 mounts per test (p = 0.0001) and structurally, as revealed by prominent clitoral hypertrophy.
The findings indicate (1) that the female fetuses and the pregnant females carrying them are markedly different in their response to T.P. and (2) that pregnant and nonpregnant females differ in their response. It is apparent that pregnancy has accompanying it some feature which prevents pregnant females from being masculinized by androgen.