The ovary is the place where the egg develops and matures. A woman is born with 1-2*106 follicles, of which about 400 eventually mature and ovulate, with most follicles undergoing apoptosis and atresia during growth. Normally, one egg matures and is ovulated during a menstrual cycle, while the rest of the immature eggs wither or atretic themselves. A mature egg survives for about 24-48 hours after ovulation and waits for the sperm to meet it during these 48 hours. If the egg meets the sperm and fertilization is completed, pregnancy is possible. If the egg does not meet the sperm, it dies naturally after 48-72 hours and loses the chance of fertilization, and has to wait until the next menstrual cycle and repeat the same process. The left and right ovaries usually ovulate and discharge one egg from one ovary. In rare cases, both ovaries ovulate at the same time, or one ovary discharges two eggs at the same time. The growth of the egg The menstrual cycle consists of a menstrual phase, a follicular phase, an ovulatory phase and a luteal phase. In the follicular phase, the follicle slowly grows from a “baby” to an “adult” in the pre-ovulatory phase, with the diameter of the follicle growing from 2-3mm to 18-22mm, which means that in the first half of the menstrual cycle, several follicles develop one after another and gradually grow to a new size, due to the effect of estrogen. That is to say, in the first half of the menstrual cycle, due to the effect of estrogen, there are usually several follicles developing one after another, gradually growing up, we through ultrasound monitoring, found that in the near-ovulation period, these follicles always have a head of the largest (diameter of about 18-22mm), and after it ruptured and ovulated other follicles were absorbed and disappeared, we call this head of the largest (diameter of about 18-22mm), the most mature follicle is called the dominant follicle. So if the diameter of the follicle is less than 18mm, it is called small follicle ovulation, so the immature egg is not conducive to pregnancy, if the diameter of the follicle is greater than 22mm before the discharge, the ability of such an egg insemination is also reduced.