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The size of the dominant follicle from the first day of the cycle to ovulation. What size should the dominant follicle be at the time of ovulation? How to determine the size of the follicle

The female body is periodically rebuilt (natural cyclical changes) due to the influence of hormones that control the complex mechanisms relating to its reproductive system (the set of organs that ensure the process of fertilization). For the onset of pregnancy, a prerequisite must be observed - the growth and normal development of ovarian follicles, which act as a kind of "container" for already

Interpretation of the concept of "follicle"

This is a small anatomical formation that looks like a gland or a sac filled with intracavitary secretions. The ovarian follicles are located in their cortical layer. They are the main reservoirs for the gradually maturing egg.

Initially, the follicles in quantitative terms reach significant values ​​​​in both ovaries (200 - 500 million), each of which, in turn, contains one germ cell. However, for the entire time of puberty, women (30-35 years old) reach full maturity only 400-500 copies.

Internal processes of follicle evolution

They flow in their sacs and are characterized by the multiplication of granular or granular cells that fill the entire cavity.

Then the granular cells produce a fluid that pushes and pushes them apart, while directing them towards the peripheral parts of the follicle (the process of filling the internal cavity with follicular fluid).

As for the follicle itself, it significantly increases both in size and in volume (up to a diameter of 15-50 mm). And in terms of content, it is already a liquid with salts, proteins and other substances.

Outside, it is covered with a connective tissue sheath. And it is precisely this state of the follicle that is considered mature, and it is called the Graaffian vesicle (in honor of the Dutch anatomist and physiologist Renier de Graaf, who discovered this structural component of the ovary in 1672). A mature "bubble" interferes with the maturation of its counterparts.

How big should a follicle be?

With the onset of puberty (14-15 years), he completely completes his development. It is considered normal if during the follicular phase, when the menstrual cycle begins, several follicles mature in both ovaries, of which only one reaches a significant size, which is why it is recognized as dominant. The remaining specimens undergo atresia (reverse development). The product of their vital activity is estrogen - a female sex hormone that affects fertilization, childbirth, as well as calcium content and metabolism.

The dominant follicle, which increases in size by an average of 2-3 mm every day, reaches its normal diameter (18-24 mm) at the time of ovulation.

Generative function as a priority

On the inside, a mature follicle is lined with a multi-layered epithelium, it is in it (in a thickened area - an oviparous tubercle) that a mature, fertilizing egg cell is located. As mentioned above, the normal size of the follicle is 18-24 mm. At the very beginning of the menstrual cycle, its protrusion (resembling a tubercle) is observed on the surface of the ovary.

Due to a number of hormonal disorders, this gap may be absent, and therefore the egg does not leave the ovary and the process of ovulation does not occur. It is this moment that can become the main cause of infertility and dysfunctional bleeding of the uterus.

Folliculometry: definition, possibilities

This is an ultrasound diagnostic study, through which tracking the development and growth of follicles is available. Most often, women resort to it, suffering from infertility or menstrual irregularities. The considered manipulation allows using ultrasound to track the dynamics of ovulation.

At the beginning of the menstrual cycle, it becomes possible to observe the process of endometrial growth, and in a later period, the evolution of the follicle. So, you can determine the exact size of the follicles by day of the cycle.

When is folliculometry required?

This diagnostic study allows you to:


The value of indicators of the norm and pathology of the development of the follicle

At the very beginning of its evolution, the indicator in the “norm” status is the size of the follicle in diameter of 15 mm. Further, as mentioned earlier, it increases per day by 2-3 mm.

Many women are interested in the question: “What is the size of the follicle during ovulation?” Normally it is considered - about 18-24 mm. Then the corpus luteum appears. At the same time, the level of progesterone in the blood is necessarily increased.

A single ultrasound is unable to build a complete picture of the development (maturation) of the follicle, since it is especially important to control each individual stage.

The main pathologies that disrupt the maturation of follicles are:

1. Atresia - involution of a non-ovulated follicle. To be precise, after formation, it develops up to a certain point, and then freezes and regresses, thus ovulation never occurs.

2. Persistence - the persistence of the virus, when it is still functionally active, in the cells of tissue or organism cultures over the period characteristic of an acute infection. In this case, the follicle is formed and develops, but its rupture does not occur, as a result of which it does not increase. This form of anatomical formation is preserved until the very end of the cycle.

3. Follicular cyst - a kind of functional formation, localized in the ovarian tissue. In this situation, the unovulated follicle does not rupture, it continues to exist, and fluid most often accumulates in it, and subsequently a cyst larger than 25 mm is formed.

4. Luteinization - the formation of a corpus luteum, which sometimes forms without rupture of the follicle, which subsequently also develops. This situation is possible if there was an earlier increase in the LH value or damage to the structure of the ovary.

Follicle sizes by day of cycle

From the very first days of the next cycle, with the help of ultrasound, one can notice that there are several antral anatomical formations under consideration in the ovaries, which will subsequently grow. Their increase is due to the influence of special hormones, the main ones being (FGS) and estradiol. Provided that their level corresponds to the established norm of the content of these substances in the blood, a woman most often has stable ovulation, and anovulatory cycles are observed no more than twice a year.

After the moment when the size of the follicles during stimulation according to the first scheme reaches 18 mm in diameter (at 8 mm), triggers are introduced (drugs that simulate the release of LH). Then, after the introduction of hCG, ovulation occurs approximately two days later.

The second scheme of manipulation is applicable mainly to women who have a low and low probability of the effect of small doses of FSH.

Mandatory indications for this manipulation:

  • female age over 35 years;
  • FSH value over 12 IU / l (on the 2nd-3rd day of the cycle);
  • ovarian volume up to 8 cu. cm;
  • secondary amenorrhea and oligomenorrhea;
  • the presence of operations on the ovaries, chemotherapy or radiotherapy.

A visible result should appear by the sixth day. A significant side effect affecting the ovaries during this ovulation is the risk of their hyperstimulation syndrome. In the case when, during the next ultrasound, follicles in the ovaries are detected, the size of which exceeds 10 mm in diameter, the doctor regards this as a signal to carry out preventive procedures for this syndrome.

Control ultrasound examination

It is necessary to confirm ovulation through transvaginal ultrasound. This is as important as the monitoring itself. It was previously mentioned what size the follicle is before ovulation (18-24 mm in diameter), however, even when the required size is reached, the capsule may not break through, and the mature egg will not be released into the abdominal cavity. Control ultrasound is performed 2-3 days after the estimated moment of ovulation.

At this session, the doctor will check the condition of the ovaries for signs of ovulation that has taken place:

  • the dominant follicle is absent;
  • a corpus luteum is present;
  • there is some fluid in the space behind the uterus.

It is important to note that if the specialist conducts a follow-up ultrasound at a later period, he will no longer detect either fluid or corpus luteum.

Finally, it would be useful to once again answer the question: “What is the size of the follicle during ovulation?” This dominant anatomical formation at the time of ovulation matures to a size of approximately 18 - 24 mm in diameter. It is worth remembering that the size of the endometrium and follicles varies depending on the day of the menstrual cycle.

To help everyone who wants to know how the follicle grows and what size it reaches during ovulation, so that a full-fledged cell comes out of it, our article.

Follicle sizes at different stages

Ovulation is a short period of the menstrual cycle, which plays a major role in the process of conception. It is characterized by the exit of the female cell into the genital tract. And here already, under a favorable set of circumstances, fertilization by a spermatozoon will occur.


In general, the cycle consists of two more stages, between which ovulation is located. The first is called follicular. Its duration varies for each lady and can be 11-21 days. At this time, the development of the follicle, in which the cell is formed, occurs. When it reaches the desired size, it breaks through the follicle and goes into the fallopian tubes.

In the ovaries every month, immediately after menstruation, several follicles begin to grow at the same time, their size gradually changes:

  • the initial size of each follicle is 1-2 millimeters;
  • by 5-7 days there is growth up to 2-6 mm;
  • by 8-10 days, one of them overtakes the others, having a size of 12-15 mm, while its growth rate is much higher;
  • the remaining bubbles begin to decrease and gradually disappear;
  • the leader continues to grow by 2-3 mm per day.

You can observe the growth of a liquid bubble on ultrasound. It can reliably indicate at what size of the follicle ovulation occurs. The doctor controls the process and reports the most favorable moments for fertilization.


All other methods for determining the day of release of the cell will not be able to help in this matter. Neither the measurement of basal temperature, nor tests, will tell you what size the follicle should be before ovulation, and the saliva device is powerless in this.

Therefore, as the only truthful study, ultrasound starts from 8-10 days at a regular rhythm of 28 days and continues at intervals of 2 days, noting how development occurs and what size the follicle has reached before ovulation. The bubble diameter by 12-14 days is 24 mm.

Observing such parameters, it is necessary to prepare for this moment. If a woman is planning a pregnancy, she should intensify her sexual life. We know that our cell does not have a long life span. The known maximum today is 36 hours. And on average, she lives about a day. During this time, she makes her way to the right place in the fallopian tube, where she will be met by a male cell. Spermatozoa, or rather some of them, are able to hold out for 2-3 days. Therefore, it is advised to carry out sexual intercourse for a full-fledged conception the day before (a day before the desired day) or 2-3 days in advance, and not only during ovulation.

Why the size of the follicle may not reach the norm

The growth of the liquid bubble, and directly on what size the follicle reaches during ovulation, is influenced by various factors:

  • stress;
  • hormonal disorders;
  • long-term use of contraceptive drugs;
  • violations in the functioning of the thyroid gland;
  • the presence of prolactin in the blood during breastfeeding.

All this can disrupt the menstrual cycle, shift the moment of cell release for a long time, due to which it is observed to be late. At the same time, the calculations of the desired day are not relevant, which complicates the process of conception.

Therefore, in order to avoid problems in the form of infertility, a woman needs to control the cyclicity of her rhythms, pay attention to the regularity of "critical days", use known methods to detect ovulation. At the slightest failure, you need to look for the cause with the help of a doctor and eliminate it as soon as possible.

Having studied the basic standards and parameters, what size should the follicle be for ovulation, do not forget that the processes in the body are unique and the indicators may vary due to external factors.

For a normal conception, a full-fledged and timely mature cell and a healthy, mobile sperm are needed. To get these components, you need to lead a healthy lifestyle, eat rationally, try to get rid of stress, monitor the condition of your genitals, and then the joy of motherhood will become quite real.


Remember that solving a small problem in the form of a hormonal disorder is much easier than treating infertility. Listen to the signals of your body and even with a slight deviation from the normal rhythm, do not be too lazy to visit a gynecologist. In any case, the doctor will tell you what size the follicle has reached during ovulation, and how much is enough for a successful conception.

The growth of the follicle and the subsequent ovulation of the mature egg in it are key processes that ensure the readiness of the female reproductive system for conception. Violation of this natural mechanism is one of the most common causes of infertility. And all IVF programs include a stage of stimulation of follicle growth to induce hyperovulation.

Depending on the protocol used, it is performed on the biological mother or on the egg donor. At the same time, folliculometry is required to track the number of maturing follicles, their size and readiness for ovulation.

A bit of theory

Follicles are called special formations in the ovaries, consisting of an oocyte of the 1st order (an immature egg) and several layers of special cells surrounding it. They are the main structural formations of the female gonads, performing endocrine and reproductive functions.

Follicles are laid in utero. They are based on oogonia - primary germinal germ cells that migrate to the germinal ovary at about 6 weeks of gestation. After meiotic division and proliferation, these precursors form first-order oocytes. These immature germ cells are covered with cuboidal epithelium and form the so-called primordial follicles. They will remain in a dormant state until the onset of the sexual development of the girl.

Subsequently, primordial follicles are successively transformed into preantral, antral, and preovulatory follicles. This process is called folliculogenesis. Normally, it ends with ovulation - the release of a mature and ready for fertilization egg. In place of the follicle, an endocrine-active corpus luteum is formed.

At the onset of conception, it is stored under the action of chorionic gonadotropin. Progesterone produced by them contributes to the prolongation of pregnancy. In all other cases, the corpus luteum is reduced, which occurs before menstruation. The accompanying sharp drop in progesterone levels provokes the onset of menstruation with rejection of the overgrown glandular (functional) layer of the endometrium.

A situation is possible when a mature follicle does not ovulate. At the same time, it can continue to increase in size, transforming into a reduced egg. Such formations can be single and gradually absorbable. But sometimes cysts persist for a long time, deforming the surface of the organ. In this case, one speaks of . Such a diagnosis is prognostically unfavorable for conception, it is usually accompanied by persistent dyshormonal disorders and infertility.

How many follicles are in the ovaries?

Not all ovarian follicles initially laid in utero are preserved by the time of puberty and subsequently develop. About 2/3 of them die and resolve. This natural process is called apoptosis or atresia. It begins immediately after the laying of the gonads and continues throughout life. A girl is born with approximately 1-2 million primordial follicles. By the beginning of puberty, their average number is 270-500 thousand. And during the entire reproductive period, only about 300-500 follicles ovulate in a woman.

The sum of all follicles capable of further development is called the ovarian reserve. The duration of the woman's reproductive period and the onset, the number of productive (with ovulation) menstrual cycles and, in general, the ability to re-conceive depend on it.

The process of progressive depletion of the ovarian reserve in the ovaries is noted on average after 37-38 years. This means not only a decrease in a woman's ability to naturally conceive, but also the beginning of a natural decrease in the level of basic sex hormones. The cessation of the development of follicles in the ovaries means the onset of menopause. It can be natural, early and iatrogenic.

Graafian bubble formation phase

The amount of follicular fluid progressively increases, it pushes the entire epithelium and the egg to the periphery. The follicle grows rapidly and begins to protrude through the outer shell of the ovary. The egg in it is located on the periphery on the so-called egg-bearing mound. Approximately 2 days before ovulation, the amount of secreted estrogen increases significantly. This feedback triggers the release of luteinizing hormone from the pituitary gland, which triggers the ovulation process. A local protrusion (stigma) appears on the surface of the Graafian vesicle. This is where the follicle ovulates (ruptures).

As a result of ovulation, the egg, ready for fertilization, leaves the ovary and enters the abdominal cavity. Here she is captured by the villi of the fallopian tubes and continues her natural migration towards the spermatozoa.

How is the “correctness” of folliculogenesis assessed?

The stages of folliculogenesis have a clear relationship with the days of the ovarian-menstrual cycle. Moreover, they do not depend on the age and race of the woman, but on her endocrine status.

The growth and development of the follicle is primarily regulated by the follicle-stimulating hormone of the pituitary gland. It begins to be produced only with the onset of puberty. At a certain stage, folliculogenesis is additionally controlled by sex hormones, which are produced by the cells of the wall of the developing follicle itself.

Any hormonal imbalance can disrupt the process of maturation and ovulation of the egg. At the same time, determining the level of hormones does not always provide the doctor with all the necessary information, although it allows you to identify key endocrine disorders. Therefore, the diagnosis of violations of the folliculogenesis process is the most important stage in the examination of a woman at the stage of pregnancy planning and in identifying the cause of infertility.

At the same time, the doctor is interested in how large the follicle grows and whether it reaches the stage of the Graafian vesicle. Be sure to monitor whether ovulation occurs and whether a corpus luteum of sufficient size is formed. In anovulatory cycles, the maximum size of developing follicles is determined.

An accessible, informative and at the same time technically simple method is. This is called monitoring the maturation of follicles using ultrasound. It is performed on an outpatient basis and does not require any special preparation of the woman. Folliculometry is a dynamic study. Several repeated ultrasound sessions are required to reliably monitor changes occurring in the ovaries.

In the process of folliculometry, the specialist determines the number, location and diameter of maturing follicles, monitors the formation of a dominant vesicle, and determines the size of the follicle before ovulation. Based on these data, you can predict the most favorable day of the cycle to get pregnant naturally.

With IVF protocols, such monitoring allows you to evaluate the response to ongoing hormonal therapy, set a date for the introduction of drugs to stimulate ovulation and subsequent puncture egg retrieval. The key parameter of folliculometry is the size of the follicle by day of the cycle.

Norms of folliculogenesis

Folliculometry is performed on certain days of the cycle, corresponding to the key stages of folliculogenesis. The data obtained during repeated studies are compared with the average statistical norms. What size of the follicle should be on different days of the ovarian-menstrual cycle? What fluctuations are considered acceptable?

Normal follicle size on different days of the cycle for a woman aged 30 years with a 28-day cycle, not taking oral contraceptives and not receiving treatment with hormonal stimulation of ovulation:

  • On days 1-4 of the cycle, several antral follicles are found, each of which does not exceed 4 mm in diameter. They can be located in one or both ovaries. Their number depends on the age of the woman and her ovarian reserve. The norm is if in both ovaries a total of no more than 9 antral follicles mature simultaneously.
  • On the 5th day of the cycle, antral follicles reach a size of 5-6 mm. Their development is quite uniform, but already at this stage atresia of some vesicles is possible.
  • On the 7th day, the dominant follicle is determined, its size is on average 9-10 mm. It is he who begins to actively develop. The remaining bubbles will gradually decrease, while they can be determined in the ovaries and during ovulation.
  • On the 8th day of the cycle, the size of the dominant follicle reaches 12 mm.
  • On day 9, the bubble grows to 14 mm. It clearly defines the follicular cavity.
  • Day 10 - the size reaches 16 mm. The remaining bubbles continue to decrease.
  • On day 11, the follicle increases to 18 mm.
  • Day 12 - the size continues to grow due to the follicular cavity and reaches 20 mm.
  • Day 13 - Graafian vesicle with a diameter of 22 mm (this is the minimum size of the follicle for ovulation in the natural cycle). On one of its poles, a stigma is visible.
  • Day 14 - ovulation. Usually the follicle bursts when it reaches 24 mm in diameter.

Deviations from these normative indicators in the direction of decrease are prognostically unfavorable. But when evaluating the results of folliculometry, the duration of the woman's natural cycle should be taken into account. Sometimes early ovulation occurs. In this case, the follicle reaches the required size for 8-12 days of the cycle.

IVF follicle size

With IVF protocols, ovulation is drug-induced and pre-planned.

On different days of the menstrual cycle, the follicles have a certain size, as they mature, they increase, and before menstruation they break, releasing the sex cell. Knowing about the change in the diameter of the follicular tissue is important, as it helps to calculate the period of ovulation, as well as determine the parameters of the health of the woman's reproductive system. What is the size of the follicle on the days of the cycle and why can it stop growing?

The "rudimentary" sex cells are laid in the body of every girl even before her birth, there are about 8-10 thousand of them inside the ovaries. But initially, such rudiments are not yet ready for fertilization, because they must go through several successive divisions for maturation. To protect the egg during its growth and transformation, several layers of epidermal tissue grow around it - this is the follicle, which resembles an epithelial cocoon.

Follicular tissue is under the influence of the endocrine system, its increase and development is regulated by the hormones of the ovaries themselves, as well as the pituitary gland, an indirect effect is observed from the adrenal glands. For example, FSH (follicle-stimulating hormone) stimulates the maturation of primordial (rudimentary) follicles during adolescence and on different days of the menstrual cycle, and LH (luteinizing) helps to accelerate their growth for further release of the germ cell before ovulation.

Size by day of cycle

The size of the follicle changes on different days of the menstrual cycle. After the end of menstruation, under the influence of the active substances of the ovaries and pituitary gland, the development of several epithelial cocoons (up to 6-7 pieces) begins, but by the eighth day after the onset of development, a dominant follicle appears, in which the gene activity was the highest, so it reached the mark of 8 the fastest. -10 mm. The remaining epithelial cocoons may stop growing or undergo apoptosis, that is, planned cell death.

Dominant follicle development

After that, the body "concentrates" on this dominant follicle, and the growth of the rest stops to save nutritional resources and energy. Every day before ovulation, there is an increase in this epithelial cocoon for the egg by 1.5-2 mm in diameter. During this period, the egg begins to mature, undergoes several successive divisions, during which nutrients are concentrated inside it, the necessary membranes appear (there are 3 of them in the egg).

On the 11th day of the cycle, the size of the follicle is about 15-16 mm, after which its growth slows down a bit. During this period, the egg is already at the final stage of its development, preparation for ovulation begins. On which day it happens depends on the activity of the endocrine system and the state of health of the woman, usually this happens on the 15-16th day.

On the 15th day of the cycle (sometimes there are shifts of 2-3 days), the follicle reaches 22-24 mm in diameter and a critical point occurs, since it can no longer grow, so the epithelial cocoon breaks and the sex cell comes out - into the abdominal cavity, and then into the fallopian tubes.

It is during this period, which will last only 36-50 hours, that fertilization can occur. But it is important to understand that under the influence of hormones, ovulation, that is, the release of an egg, can occur sooner or later. If you observe the follicular tissue during the ovulatory phase, you can see how the epithelial cocoon increases dramatically, the egg is released, and after that it decreases, only its remnants (yellow body) are visible.

Follicle Growth Chart

After reading a short information about, the algorithm itself becomes clear, but it is difficult to understand the exact data, so below is a simple table that shows the size of the epithelial coating of the egg on different days of the menstrual cycle.

The indicators presented in the table are the established norm for the development of follicles on the days of the cycle, but it is not in vain that the gynecologist, in order to prescribe contraceptives or determine “safe” days of the cycle, checks the size data for the girl individually, because the rate of maturation and growth of the egg in the follicular cocoon depends on her heredity , the work of the endocrine system, the level of stress and even weight.

Why does the follicle not grow

The lack of growth and development of follicles is one of the most common causes of infertility in women. Deviation from the norm of development of follicular tissue may appear due to:

  • disturbances in the work of the pituitary and hypothalamus;
  • dysfunction or underdevelopment of the ovaries;
  • the appearance of cysts in the ovaries or the presence of multifolliculosis;
  • inflammatory or infectious processes in the organs of the reproductive system;
  • hormonal imbalance;
  • the appearance of cancerous neoplasms in the mammary glands, pituitary gland or ovaries;
  • frequent stressful effects on the body, severe depression;
  • dramatic weight loss, BMI below 17.5;
  • early menopause.

It’s worth starting with a hormonal imbalance, which becomes the main reason for stopping the growth of follicles in the ovary. With tumors or dysfunction of the pituitary gland in the body of a girl, there is a lack of the hormone FSH, and the regulation of the release of active substances by the ovaries and thyroid gland is also disrupted. The same effect of inhibiting the development of follicles is observed with underdevelopment or poor functioning of the ovaries.

If a girl has too low weight or there are infections of the reproductive system, the body “understands” that she will not be able to bear the child, so there is no need for ovulation and follicle growth. After STD treatment or weight gain, the follicular growth cycle usually returns to normal.

During stressful periods or prolonged depression, the girl's adrenal glands secrete more than the norm of the stress hormone - cortisol, which increases the risk of miscarriage of the fetus, so follicles will not develop in such an environment. Restoring their growth in such a situation is not so easy, it can take several months until the hormonal background stabilizes.

The growth of follicles continues from the beginning of the menstrual cycle until ovulation. First, several epithelial cocoons develop, but already on the 8-9th day, one dominant one is released, and the rest stop growing. The growth of follicular tissue lasts until ovulation, during which it ruptures and releases a mature egg. But with various disorders in the body, the follicular cycle can be suspended.

Ask a Question!

You have questions? Feel free to ask any! And our in-house specialist will help you.

What is a dominant follicle? The answer to this question should be known to any woman who is interested in the structure of her body, and even more so at the stage of pregnancy planning. Find out the structure, functions, stages of maturation, size and other important and interesting points.

The female reproductive system is complex. The basis of future life is the sex cell, called the egg. Every month, she matures in the ovary, in order to then leave it and unite with the spermatozoon for the birth of a new life. Functions of protecting immature eggs (oocytes) are performed by the functional follicular cells surrounding them and located in the outer layers of the appendages, which later transform to fulfill their main purpose.



What day to do an ultrasound to find out if the follicle is maturing?

At the beginning of the menstrual cycle, follicular cells begin to rapidly develop and form vesicles. One of them grows faster than the others: it is dominant, and it is in it that the maturing and preparing for fertilization egg is located. At the same time, the rest pass into involution, that is, they return to their previous initial state.

Follicles are formed even before the birth of a girl.
The total number is about 1 million, but some are destroyed, and by the time puberty is completed, about 200-300 thousand remain. But for the entire reproductive period, no more than 500 pieces manage to fully mature, the rest are destroyed and excreted from the body.

Stages of development

Over the entire period of a woman's life, starting from birth, follicles go through several stages of development:

  1. primordial stage. These are immature follicular cells that are laid down during the formation of a female fetus. They are very small and do not exceed 0.05 mm in diameter. Follicles capable of dividing are covered with epithelium and pass to the next stage.
  2. Primary or preantral formations reach 0.2 mm in diameter. During the active puberty of a girl, the pituitary gland actively synthesizes folliculotropin, which accelerates the development of cells, strengthens their membranes and forms a protective layer.
  3. Secondary or antral follicles increase in size up to 0.5 mm. Their total number is about 8-10. Under the influence of estrogens, the internal cavity begins to fill with fluid, which stretches the walls and provokes the rapid growth of bubbles. Secondary follicles, by the way, are considered temporary organs of the endocrine system that produce hormones.
  4. As a rule, only one follicular formation passes to the next stage - the dominant one. It becomes the most voluminous and contains an almost completely mature and ready-to-fertilize egg. The vesicle consists of a large number of granulosa cells and is designed to provide reliable protection of the oocyte until the moment of ovulation. The remaining secondary follicles at this time synthesize estrogens, which ensure the rapid development of the main vesicle.
  5. The tertiary or preovulatory vesicle is called the Graaffian vesicle. The follicular fluid completely fills its cavity, its volume increases a hundred times compared to the original. During ovulation, the vesicle ruptures and an egg is released from it.

Ripening in every menstrual cycle

From the beginning of the menstrual cycle, about 8-10 secondary follicles are formed in both ovaries. From about the eighth or ninth day of the cycle, the bubbles begin to fill with the liquid formed under the influence of estrogen synthesized by the female body. And already at this stage, the dominant follicle is noticeable: it is larger than the others, and this can be seen on ultrasound.


The bubble continues to fill with fluid, stretches and bursts at the time of ovulation. A mature egg is released, which will begin to move along the fallopian tube to the uterus to connect with the sperm. What day does the break occur? It depends on the duration of the menstrual cycle: if it lasts 28-30 days, then ovulation and, accordingly, the release of the egg from the burst follicle falls on the 14-16th day (the countdown is from the beginning of menstruation).

In place of the ruptured vesicle, a corpus luteum is formed - a temporary endocrine gland that actively synthesizes progesterone and ensures the preparation of the uterus for a possible pregnancy. The hormone produced makes the endometrium loose and soft so that the fetal egg can firmly gain a foothold in it and begin to develop.

Normal sizes

What is the size of the dominant follicle? It grows from the beginning of the menstrual cycle until ovulation, and its diameter is constantly changing. Consider the norms for different periods:

  • From the 1st to the 4th day of the cycle, all bubbles are approximately the same size - about 2-4 millimeters.
  • On the fifth day, the diameter reaches 5-6 mm.
  • On the 6th day, the bubble will grow to 7-8 mm in diameter.
  • By the seventh or eighth day, the follicle will reach a size of about 10-13 millimeters.
  • On the 9-10th day, the diameter increases to 13-17 mm.
  • By the 11-12th day, the size increases to 19-21 mm.
  • Before ovulation, the diameter can be about 22 mm.
  • During ovulation, the dominant follicle is 23-24 mm in size.

Normally, active growth begins approximately from the fifth day of the menstrual cycle and is about two mm per day.

In which ovary will the dominant follicle mature?

The dominant follicle can mature both in the left ovary and in the right one. In healthy women who do not have pathologies and diseases of the reproductive system, the appendages function fully and alternately. That is, if in the last cycle the mature egg left the follicle of the right ovary, then in the next menstrual cycle the oocyte will mature in the left appendage.


Scientists have noticed that most often the dominant follicle matures in the right ovary. Some researchers have associated this with a more active innervation of this side in right-handers, which is the vast majority of women. In other words, the right side is more functional, so the right appendage is better supplied with blood and oxygen, which stimulates the maturation of the bubble.

A rarer occurrence is two dominant follicles that have formed simultaneously in both ovaries. In this case, a multiple pregnancy is possible, and the born twins will be fraternal and not similar to each other. Theoretically, conception by two different biological fathers is possible if the follicles do not mature at the same time, and the eggs are released at different times with a certain interval.

Possible pathologies

Consider some deviations from the norm:

  • The dominant follicle is absent. This suggests that there will most likely not be ovulation in the current menstrual cycle. Every healthy woman has anovulatory cycles once or twice a year. If there is no ovulation for several months in a row, this is not normal.
  • Multiple follicles or the so-called multifollicular ovaries is a deviation that develops as a result of hormonal disorders. The dominant follicle may be absent or develop slowly, which will reduce the chance of conception.
  • The formation of cysts. The dominant follicle does not burst, overflows with fluid and stretches, forming a benign formation - a cyst (it can grow or regress on its own, that is, burst and disappear).
  • Atresia - slowing down, stopping the growth of the main vesicle and its subsequent death without the release of a mature egg.
  • Persistence. The dominant follicle reaches the desired size, but does not break and remains intact until the onset of menstruation. Conception becomes impossible.
  • luteinization. The corpus luteum begins to form when there is a whole follicle in the ovary.

These pathologies are visible on ultrasound and are caused by hormonal disruptions or diseases of the reproductive system.

The dominant follicle is essential for fertilization. But conception will occur if the bubble forms correctly, and a mature egg comes out of it. The information presented in the article will help to understand the mechanism of fertilization and identify some problems.

    • Discussion: 12 comments

    Hello. Ultrasound of the follicle on the 13th 14th 15th day. Does it make sense to take 3 days in a row?

    Answer

    1. Yes, it makes sense to conduct an ultrasound every two to three days. Also for monitoring the endometrium to predict the date of ovulation.

      Answer

    Hello, there was a delay of 2 weeks, then the menstruation went, but 2 days before them, the right ovary began to pull a little. This continued during menses. And now they have already ended, but the pulling pain has not disappeared. On the seventh day of the cycle, I went for an ultrasound, they said that everything is fine, in the right ovary the dominant follicle is 16 mm. They said that the pain is possibly related to the growth of the follicle. Is this true, and when will the pain go away?

    Answer

    1. Hello, Natalia! Yes, this is usually due to the growth of the dominant follicle. If the pain will be prolonged, it is worth being examined for the presence of pathologies of the reproductive system.

      Hello! 11 months have passed since the second birth. I am breastfeeding my baby. I drank Lactinet, menstruation came to the abolition. On the 15th day, she underwent follicullometry, the diagnosis was MFN, there was no dominant follicle. They were like that even before pregnancy. The cycle was extended, up to 50 days happened. Pregnant to cancel OK. Ovulation occurred at 16 dmc and 18 dmc Question: is ovulation possible in this cycle if there is no dominant follicle on ultrasound on the 15th day?

      Answer

      1. Hello Amina! Unfortunately, ovulation is impossible without a dominant follicle, but don't worry, it may appear in the next cycles. Take care of your health, eat right, and if necessary, consult with your doctor about resolving this issue. You may need to take tests, including hormones, as well as change your lifestyle to prepare the body for conception and pregnancy.

        Answer

      2. Hello, help me figure it out, we plan to conceive a girl three days before the release of the egg. Cycle 29-31 days, 11 dc folliculometry showed a dominant follicle of 11 mm and the doctor said that the release of the egg will be on the 15-16th day. PA was at 13 dts early in the morning, exactly three days before the exit !!!, immediately the lower abdomen began to pull, the egg white increased (usually 2-3 days before O), and at 16-00 there were brown streaks on the linen, on 14 ds, pulling, throbbing pains continued and at 17-00 folliculometry showed that the follicle had begun !!! release fluid, the doctor said that free fluid was being scanned around the ovary and that ovulation had just begun. QUESTION: did it really start today (14 dts) or did it start on 13 dts, because If 13 then the Y chromosomes will definitely have time ((((, and if 14 then more than 30 hours have passed and the Y chromosomes died and X chromosomes remained (girls)))))

      Answer

      1. Hello Nina! It is worth trusting the doctor's words, and in your case, the probability of conceiving a girl is still greater, since the X chromosomes live up to 5 days. During the day or at the time of ovulation, there is a greater chance that there will be a boy.

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