Follicle size and onset of ovulation

Women who have been planning to conceive a long-awaited baby for a long time are gradually mastering a lot of medical terms that women who do not have problems with conception sometimes do not even know about. One such term refers to the size of the follicle on different days of the cycle and during ovulation.

What it is?

The growth rate of bubble formations located on the surface of the female genital glands is a very important process that affects a woman's fertility, her ability to bear children. Any violation of this process threatens with infertility. Follicles begin to mature in a healthy woman at the beginning of a new menstrual cycle. There are several... Under the influence of hormonal support of this process one follicle remains dominant (rarely two), inside which a germ cell develops - oocyte, which is also called an ovum. When the bubble reaches the desired size, under the action of luteinizing hormone, it ruptures - ovulation. In this case, the egg leaves the follicle and enters the fallopian tube, where it will meet with the male reproductive cells.

It is very important to monitor all these processes for women who have not been able to get pregnant for a long time, as well as for those who have entered the IVF protocol. The growth rate of the follicle in this case is determined by ultrasound, its size is fixed, which gives the doctor the opportunity to predict the timing of ovulation.

The follicle itself is a formation that resembles a bag for an egg maturing inside. It has shells, inside it there is a nutrient fluid, in which the oocyte matures.

Follicles are formed in a girl even when she herself is in the mother's womb. Already in the sixth week of pregnancy, they form from the embryonic sex lobes. Immature oocytes appear in them a little later, they are inactive, and before puberty they "sleep". The ovarian reserve of a newborn girl is several million oocytes, by the beginning of puberty, no more than 30% of it remains, and by the age of 30 - no more than 10%... Some of the cells die from the action of unfavorable factors - diseases, ecology. The rest must ensure the fertility of the girl and the woman throughout their lives.

As soon as the girl starts menstruating, every month the egg matures in succession, which lives for a day, and if conception does not occur, it dies and after two weeks menstruation begins. So the cycle repeats over and over. The ovarian reserve is not replenished during life, and when the number of follicles is depleted, menopause occurs.

After the follicle ruptures during ovulation, a corpus luteum forms in its place, which takes on temporary responsibilities for the production of progesterone. If pregnancy has come, then other endocrine active structures will do this, if not, then the corpus luteum dies, progesterone falls, menstruation begins.

Sometimes during ovulation the follicle does not rupture, ovulation naturally does not occur... This follicle becomes a cyst. Solitary cysts are often physiological in nature, they are not dangerous for a woman and are favorable in planning pregnancy. But if too many of them are formed, the ovaries become polycystic, which is a common cause of infertility in women.

How does folliculogenesis occur?

At birth, girls have up to 2 million follicles in their ovaries. Two thirds of this amount perishes and resolves independently and asymptomatically. By the beginning of puberty, the number of follicles in a girl usually does not exceed 500 thousand. Ovulation ends the existence of approximately 500 follicles in a lifetime... This is an ovarian reserve, which can be more or less than the indicated numerical expressions, depending on the individual fertile ability of the fair sex. Their number directly depends on how long a woman can maintain the ability to become pregnant and carry a baby, as well as the timing of the onset of menopausal changes.

After 37 years, the depletion of the reserve begins to pass at a faster pace, fertility and the level of production of sex hormones decrease.

During the reproductive period, a woman has a growth of follicles every month. At the initial stage, at the beginning of the cycle, the oocyte begins to grow, it acquires a zona pellucida, the neighboring cells surrounding the egg cell begin to produce fluid in order to provide a nutrient medium. The fluid is limited by the walls of the follicle membrane. One follicle can grow, the rest will be left by the body "for the future." If the maturation of two oocytes and double ovulation occur at the same time, then a woman can become a mother of twins or triplets (if one of the eggs after fertilization doubles, division into two is the same).

Follicle size

During growth in the first half of the menstrual cycle, after the formation of a bubble with liquid, the follicle begins to grow actively, the female reproductive cell itself shifts to the periphery, the follicle protrudes above the surface of the ovary, and therefore can be seen and recorded during an ultrasound examination of the sex glands.

A couple of days before ovulation, a peak concentration of estrogen is recorded in a woman's body, which provokes the active production of lutheralizing hormone, which should lead to rupture of the follicle. Under the influence of the hormone, the follicle membrane becomes uneven, a protrusion, called stigma, forms on it. It is in this place, when the time comes, that a break occurs.

To understand what phase of this process a woman is in, doctors do a blood test for FSH and LH. But without folliculometry (ultrasound of the ovaries), the idea of the size of follicles cannot be reliable and accurate... Usually, during a cycle, you need to visit an ultrasound doctor several times in order to assess the growth of follicles over time.

Norms

Before talking about whether the follicle corresponds to the size, you should know that in many respects this value is individual, although the average standards still exist. It is with them that the results of measurements based on the results of folliculometry are compared.

If a woman does not take hormonal drugs, does not undergo treatment at the moment with the use of hormonal stimulation of ovulation, then the norms are as follows.

1 - 4 days cycle (menstruation is in progress) - several maturing follicles are found, the size of each is no more than 4 mm. Such follicles, called antral, can be located in one ovary, and in two at once - there is no need to be afraid. Normally, there are no more than 9 such follicles.
5 - 6 days menstrual cycle (menstruation is over) - the follicles have grown to 5-6 millimeters. Their number remained the same or decreased due to the fact that some of the bubbles stopped developing for natural reasons.
Day 7 cycle allows you to select among all the growing dominant follicle, it differs from others in size, reaching a diameter of 9-10 mm. It is he who has to develop further. The rest of the bubbles will gradually disappear.
Day 8 menstrual cycle - the size of the dominant follicle reaches an average of 12 mm.
Day 9 cycle - the dominant follicle reaches the size of 13-14 mm, the ultrasound doctor can already visually determine the cavity with the developing egg in it.
Day 10 female cycle - the size reaches 15-16 mm.
Day 11 menstrual cycle - there is a sharp jump, the dominant follicle increases to 17-18 mm.
12 day the female cycle, the follicle begins to increase the internal cavity, its size reaches 19-20 mm in diameter.
On the 13th day the cycle, the doctor discovers the stigma, which indicates the readiness of the bubble to rupture. The diameter reaches 22 mm, which is considered the minimum size for a cycle that is not associated with the intake of hormones, with stimulation, that is, in a natural cycle.
Ovulation - the follicle, as a rule, ruptures at a size of 24 mm.

If a woman's sizes are less than these norms on a particular day, this is considered an alarming symptom, indicating that problems with conception in this cycle are not excluded.

With IVF, ovulation is usually triggered by medication, it is planned in advance... The task of doctors in this case is to get hyperovulation, that is, several large and mature eggs. The size of the follicles in this case may differ up or down. Self-ovulation is not allowed, and if stigma is detected, eggs are taken by puncture under anesthesia and ultrasound control, so that they can then be fertilized in the laboratory.

After ovulation, the size of the follicle ceases to be recorded, from that moment doctors estimate the size of the corpus luteum formed at the site of the ruptured follicle. This is necessary to assess its viability, predict the course of pregnancy, characteristics of the second phase of the cycle in case of its failure.