The normal number of female follicles

The follicles are very important for female fertility. Only when the follicles develop normally can the eggs be successfully discharged, and only when the eggs can be successfully discharged can women conceive normally. Many women who are preparing for pregnancy will also test their follicles. So, how many follicles is normal for a woman? The following will introduce relevant knowledge to you!

1. Time of follicle appearance

At the beginning of each menstrual cycle, multiple follicles develop simultaneously, but generally only one or two follicles develop to maturity, called the primary follicles (dominant follicles), and the remaining follicles close one after another. It is reported that in more than 90% of the cycles, only one follicle grows rapidly to maturity, and 5%-11% have two main follicles develop. The earliest time for ultrasound imaging of follicles can be 5-7 days in the menstrual cycle, and the minimum diameter displayed is 4-5mm.

Second, the growth rate of follicles

Ultrasound can reveal small follicles in the ovaries on the 3rd to 5th day of the menstrual cycle. These follicles gradually grow larger, reaching their largest size on the 14th day on average, and ovulation can occur. From the 5th day of menstruation to before ovulation, the primary follicle grows an average of 1.5mm per day; before the 10th day, it grows an average of 1.2mm per day; 4 days before ovulation, it grows an average of 1.9mm until the follicle matures.

Characteristics of mature follicles

① The follicle is round or oval, with a diameter of 15-30mm (21.2+-0.53mm). The follicle is echo-free, clear and pure, with clear boundaries and thin walls. ② One day before ovulation, 20% of the mature follicles can be seen as a cumulus oophorus image, which appears as a short and strong echo near the wall of the follicle.

4. Ultrasound image of ovulatory follicles

① The appearance rate of cumulus ova is about 20%, mostly appearing in mature follicles >18mm, and ovulation is predicted to occur within 24 hours. ② The sonic ring around the follicle is formed as the LH value rises, the membrane tissue edema, and the granulosa cells separate from the theca cells. Ovulation is predicted to occur within 24 hours. Ultrasound currently shows that the chance is very low. ③ The granulosa cells of the follicle wall are completely separated from the bottom layer of the membrane tissue, and the follicle wall appears serrated.

5. Number of follicles

The ovarian follicle is composed of an oocyte and many small follicular cells around it. According to the morphological and functional changes in the process of follicle development, it can be divided into three stages: primordial follicle, growing follicle and mature follicle. Women are born with primordial follicles. Newborns have 700,000 to 2 million primordial follicles on both sides of the ovaries, and by puberty there are about 40,000 primordial follicles.

In each menstrual cycle, only one follicle is produced to maturity, which is called the dominant follicle. Other follicles are inhibited by inhibitory factors (Inhibin), stop growing, and degenerate into atretic follicles. The mature dominant follicle grows rapidly, reaching a diameter of 20 mm, and gradually migrates to the surface of the ovary. The proximal part has no blood vessels and is translucent cone-shaped, called the ovulation spot (Stigma), which protrudes from the surface of the ovary in preparation for ovulation.