Folliculometry is a dynamic observation of the growth and maturation of follicles, as well as the development of the endometrium. Folliculometry is performed in the first phase of the menstrual cycle in order to record the fact and time of ovulation (exit from the follicle of a mature egg). The study of the condition of the follicles is performed using ultrasound. For a more accurate diagnosis, it is necessary to conduct several time-separated ultrasounds. Folliculometry helps to establish the anovulatory nature of the menstrual cycle, to identify the presence of a follicular cyst, undeveloped follicles, follicle persistence.
In the first days of the follicular phase of the menstrual cycle, several follicles begin to develop in the ovaries, and subsequently the growth of one of them begins to outpace the rest. When the dominant follicle increases to 15 mm or more, others undergo reverse development (atresia). The remaining follicle continues to grow, its diameter increases by 2-3 mm per day and reaches 18-24 mm by the time of ovulation.
In women with a cycle lasting 28 days, clinical gynecology recommends that the first ultrasound be performed immediately after the end of menstruation or on the 8-10 day of the cycle, after which the follicle development is monitored daily or every other day, depending on the results obtained. In the case of a longer or shorter cycle, the start time of folliculometry is adjusted accordingly. Observation is carried out until the release of the egg from the follicle is recorded, or, in the case of anovulation, until the next menstruation.
Diagnostic criteria of ovulation
At the time of ovulation, the size of the follicle is 18-24 mm, after the release of the egg in the ovary, the presence of a yellow body is noted, in the pelvis – a certain amount of free fluid. For a sufficiently accurate diagnosis of ovulation, a number of studies with adequate time intervals are necessary. For example, if a follicle with a diameter of 15 mm is detected, and after a week of the corpus luteum in its place, it is impossible to diagnose a full-fledged ovulation that has occurred, as well as the non-appearance of a dominant follicle (or corpus luteum) with a single ultrasound is not considered sufficient reason to make any diagnostic conclusions.
- Normal ovulation. Ovulation is recognized as normal if all diagnostic criteria are consistently identified: the dominant follicle has reached ovulatory size, after which signs of egg release were noted (the disappearance of the follicle and the release of free fluid into the pelvic cavity behind the uterus). After that, a yellow body developing at the site of the follicle is detected, and a week later, a decrease in progesterone levels is noted in the blood.
- Follicle atresia (regression). In some cases, the dominant follicle stops growing at a certain point in time (often before reaching ovulatory size) and begins to decrease (regress) without ovulation. Anovulation is indicated by the absence of fluid in the uterine space and the corpus luteum at the site of the follicle. Follicle atresia is usually accompanied by a reduced level of progesterone in the follicular phase of the menstrual cycle.
- The persistence of the follicle. If the follicle reaches the proper size, but ovulation does not occur for a long time (often until the next menstruation or more), it is said about its persistence. In this situation, signs of ovulation are also not recorded, but there is no decrease or increase in the size of the follicle for a long time. As with atresia, the level of progesterone in the first phase of the cycle is reduced.
- Follicular cyst. A follicular cyst is a non-ovulated follicle that exceeds the normal ovulatory size in diameter (25 mm or more). Echographically, it is a cavity with a liquid into which the dominant follicle, which has not been stimulated due to a lack of luteinizing hormone, is reborn. In the blood in the first phase of menstruation, a reduced level of progesterone and general estrogenism are noted.
- Luteinization of the follicle (including premature). If a yellow body begins to develop in a non-ovulated follicle, they talk about its luteinization. This happens when the luteinizing hormone is released into the bloodstream early (before the dominant follicle is fully mature). Ovulation does not occur, there are no echographic signs, ultrasound examination shows a gradual decrease in the follicle. The progesterone content in the blood is normal for the second menstrual phase.
- Follicles do not develop. Throughout the menstrual cycle, there are no signs of the development of a dominant follicle and, accordingly, ovulation. As a rule, such a picture is accompanied by a reduced level of progesterone. Variants of folliculogenesis that differ from the normal cycle require a comprehensive gynecological and endocrinological examination to identify pathologies that have caused the anovulatory cycle.