It is generally believed that pregnant female animals are not suitable for superovulation as donors, but so far there has been no literature on the effect of pregnancy on the superovulation effect of livestock. Studies have shown that the use of gonadotropin superovulation in early pregnancy can also cause normal estrus and ovulation in goats, but the estrus rate is lower than that of empty donors (50% and 83.3%, respectively). After hormone treatment, it is more obvious on Veterinary Ultrasound.

According to the theory of follicular development regulation, when there is a corpus luteum on the ovary, the secretion of progesterone by the corpus luteum will inhibit the secretion of GnRH (gonadotropin-releasing hormone) in the hypothalamus and the activity of the pituitary gonadotropin region, thereby inhibiting follicle development. Only when the corpus luteum disappears can the follicle mature and ovulate. However, during pregnancy, despite the presence of a functional corpus luteum, some livestock will also experience estrus and ovulation, and the presence of follicles can be observed on veterinary ultrasound. Similar to this situation, some people have found that under the action of exogenous gonadotropin, even if there is a functional corpus luteum on the ovary, the follicles can still mature and ovulate, and veterinary B-ultrasound can observe that the superovulated follicles can develop and mature.

After ovulation, under the action of progesterone secreted by the newly formed corpus luteum, veterinary B-ultrasound can observe that the cervix will contract and secrete a mucus plug to close the cervical opening. This mucus can prevent sperm from passing through the cervix. On the other hand, progesterone will also inhibit the peristalsis of the uterus and fallopian tubes, and this peristalsis is precisely the main driving force for sperm to move from the vagina to the fertilization site (the junction of the ampulla of the fallopian tube and the isthmus). Therefore, in theory, once the female animal is pregnant, it will cause estrus and ovulation during pregnancy due to sperm transportation problems, and fertilization cannot be achieved through this intercourse. In some individuals, sperm can still pass through the cervix, uterus and fallopian tubes from the vagina to the fertilization site normally during pregnancy. However, whether this phenomenon is an individual or a more common phenomenon needs further research and confirmation.