Observation of ovaries after delivery of ewes. In the early postpartum period, the ovaries are pulled into the abdominal cavity by the uterus, so it is difficult to monitor the ovaries with sheep B-ultrasound. The weight of the ovaries on the 7th day after delivery is 20-26% less than that on the 1st day. This weight loss may be related to the degeneration of the corpus luteum of pregnancy and the lack of development of the early follicles; the follicles grow on the 14th day after delivery, and most of them have ovulated on the 21st-25th day.

Some people performed surgery on ewes on the 28th day, and found "red bodies" left after ovulation on the ovaries. When the surgery was performed on the 40th day after delivery, corpora lutea and large follicles were found. According to the estrus cycle (17 days) of small-tailed Han sheep, it is inferred that there is a stagnation period of follicular development in the first week after delivery. This may be because the disappearance of the corpus luteum of pregnancy within 7 days after delivery hinders the development of follicles; small-tailed Han sheep can ovulate around 25 days after delivery, indicating that small-tailed Han sheep do not have an estrus period after delivery, and the ovaries show normal changes on sheep B-ultrasound. If the uterus recovers quickly, it is possible to conceive about 1 month after delivery. However, there are more cases of silent estrus or short-cycle corpora lutea in the early postpartum period, which may be related to insufficient follicular development and incomplete uterine involution. Because it is reported that there is a certain correlation between the state of the uterus and the functional activity of the ovaries in female livestock after delivery. The speed of uterine involution seriously affects the ovarian activity of female livestock after delivery. On the contrary, the slower the ovarian function recovers, the worse the effect of ovarian hormones on the activation of the uterine mucosa, which is more unfavorable for uterine involution. The recovery of the uterus can also be well observed on B-ultrasound in sheep. The ovaries and uterus also inhibit the function of the pituitary gland, so that it will not enter the estrus cycle. However, the mechanism of the correlation between the ovaries and the uterus needs further study.