Normal mature follicle size

Before doing in vitro fertilization, the doctor will remove the eggs from the woman's body and the sperm from the man's semen, combine them in vitro, and then implant them into the woman's uterus. Before extracting eggs from a woman's body, it is necessary to observe the maturity of the follicles in the woman's body, because only in this way can the eggs extracted meet health standards. Therefore, it is very necessary to have a proper understanding of how big a normal mature follicle is at this time.

Normal values ​​of mature follicle size in a normal menstrual cycle:

(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 gradually close. Some authors have 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.

(2) Follicle growth rate Ultrasound can be used to detect small follicles in the ovaries on the 3rd to 5th day of the menstrual cycle. These follicles gradually grow larger and reach their largest size on the 14th day on average, during which time 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.

Mature follicles may show the following characteristics: ① The follicles are round or oval, with a diameter of 15-30mm (21.2+-0.53mm). The follicles are 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.

(3) Ultrasound images of follicles near ovulation ① The appearance rate of cumulus ovum is about 20%, mostly appearing in mature follicles >18mm, predicting ovulation 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.