What is the corpus luteum
The body of every woman of reproductive age undergoes cyclical changes necessary for the process of conception. These processes are regulated by hormones secreted by various organs. Thus, the regularity of menstruation, which means the maturation of the egg, renewal and preparation of the inner layer of the uterus for future pregnancy, depends on hormones:
- pituitary gland;
- thyroid gland;
- ovaries;
- luteal (yellow) body.
If the first three organs are constantly present in a woman’s body, then the corpus luteum is formed and undergoes involution every menstrual cycle, accompanied by ovulation.
After the egg is ready and leaves the ovarian follicle, that is, ovulation (occurring most often on the 14th day of the cycle), the corpus luteum begins to develop in place of the burst vesicle. This is a temporary endocrine gland that produces the hormone progesterone, the main functions of which are:
- inhibition of the development of other follicles;
- improving the nutrition of the uterus by increasing the number of vessels and active blood circulation;
- stimulation of the growth of the inner (mucosal) layer of the uterus, necessary for the attachment of the egg during pregnancy;
- preparing the mammary glands for milk production;
- suppressing the effect of a woman’s immune system on the fetus.
As can be seen from the above, pregnancy and its development at the initial stage is impossible without progesterone and the gland that produces it.
Sizes of the gland on ultrasound
• If the size of the gland is 18-22 millimeters, then this is the first sign that the woman has no problems with fertilization, and this is the most opportune moment to conceive a child, since the ovulation phase has now begun. • The size of this gland on ultrasound is from 21 to 30 millimeters during pregnancy, indicating that in this case there are no problems with the fetus, and the pregnancy is proceeding well. But if the woman is not pregnant, it is called a follicular cyst. • If an ultrasound reveals this gland to be round in shape and measuring more than 40 millimeters, we are dealing with a cyst. During pregnancy, this gland can be detected up to 14 weeks; after this period, when the placenta begins to form, its function fades.
Size in early pregnancy
The development of this temporary gland occurs only with increased levels of hCG, which is observed in pregnancy. It must be remembered that the corpus luteum disappears if pregnancy does not occur. But if a woman does become pregnant, the corpus luteum will grow as the level of hCG increases. As the gland grows, the production of hormones also increases, which help with the implantation of the fertilized egg and the proper development of the fetus.
During a routine ultrasound examination, the specialist must pay attention to the size of the corpus luteum. The size of the corpus luteum normally should gradually increase. This means that the parameters at 7 weeks will be greater than at 5 weeks of pregnancy. This development is considered normal and indicates the production of the required amount of hormones. If the opposite situation occurs, then there is a risk of miscarriage. The normal size of the corpus luteum in the first trimester is from 1.5 to 3 cm, everything will be from a week of pregnancy. If a woman is not pregnant, and the size of the corpus luteum ranges from 1.5 to 2 cm, then this indicates readiness to conceive.
Detection of a corpus luteum cyst during ultrasound
Sometimes, as the placenta forms, the corpus luteum continues to grow. In this case, it turns into a cyst. This growth can even exceed 40 millimeters.
Such a cyst does not in any way affect the development of the fetus and the course of pregnancy, but if it grows beyond the permissible norm, it may be compressed, and subsequently rupture.
There are cases when an ultrasound shows a cyst of this type, even when there is no pregnancy. It is also formed from this gland at the site of a burst follicle, when its growth exceeds permissible norms. Very often, this ailment in such a situation does not bother a woman at all. Sometimes she doesn’t even know about the existence of a cyst.
Thus, ultrasound examination of the female pelvic organs is very important. And with the help of the corpus luteum, you can evaluate the reproductive function of the patient’s body (whether conception is possible or not, how the pregnancy progresses in the first trimester, and whether there is a threat of miscarriage).
Targeted identification of the corpus luteum and determination of its size at a certain phase of the menstrual cycle is carried out for:
- planning conception;
- diagnosing the cause of infertility or miscarriage;
- monitoring the normal course of pregnancy;
- diagnosis and dynamic control of luteal body cyst.
The examination can be carried out both through the abdominal wall and through the vagina, that is, transvaginally. The second method allows you to obtain more information, since with transabdominal ultrasound the ovaries are not visualized in many women.
Corpus luteum during pregnancy
The main task of the corpus luteum is to produce hormones necessary for the further development of pregnancy. Therefore, at different times it will have different sizes. In the first days of its appearance, the corpus luteum has a diameter of 15 -20 mm. Then it increases in size to 25 - 27 mm and remains this way until about the 15th week of pregnancy. After which its functions gradually cease and its size decreases.
In some women, the size of the corpus luteum during pregnancy can be more than 30 mm, in these cases they speak of a corpus luteum cyst. However, there is no reason to worry - this cyst does not pose a health hazard and does not disrupt the course of pregnancy, since it also secretes progesterone. Some expectant mothers get scared if, during an ultrasound, the doctor does not find a corpus luteum in them. But, as a rule, the problem is not at all in the woman - most often this happens when conducting research on old equipment that has low resolution, or if the ultrasound is performed by an insufficiently unqualified doctor. Simply repeat the procedure at another medical facility.
An ectopic pregnancy can be diagnosed if the following signs are detected:
- increase in the size of the uterus;
- the absence of a fertilized egg in the uterine cavity with an appropriate level of hCG and the presence of a full-fledged corpus luteum on the ovary;
- an increase in the thickness of the endometrial layer up to 20 mm, due to the stimulating effect of progesterone;
- echographic signs of the presence of a fertilized egg outside the uterine cavity (tubal, ovarian, cervical, etc. pregnancy).
As a rule, the appearance of any uncharacteristic echostructure in the area of the appendages, which has uneven or rounded contours, should be considered an ectopic pregnancy. If the site of implantation of the fertilized egg cannot be seen using an ultrasound scanner, the diagnosis is made based on indirect signs. The study of the corpus luteum is also relevant when diagnosing multiple pregnancies.
If the ultrasound showed 2 or 3 corpus luteum, then there is a high probability of the formation of 2 or more fertilized eggs. Hormonal disorders due to insufficient phase of the corpus luteum are a common cause of infertility or spontaneous abortion in the early stages.
Normal ultrasound picture
On ultrasound, the corpus luteum looks like a homogeneous structure, without cavities, with clear, even boundaries. Its presence should be determined after 12-16 days of the menstrual cycle. When pregnancy occurs, it persists until the placenta forms. If conception does not occur, it means that it is destroyed at the end of the second phase or during the beginning of menstruation.
Pathologies of this temporary organ will manifest themselves in 2 main ways:
- Violation of its formation - in this case, the corpus luteum is absent in the corresponding phase of the cycle;
- Volumetric formations (most often cysts or tumors), in which the contours and homogeneity of the organ change.
Other changes in the corpus luteum are detected extremely rarely on ultrasound.
Pathology of the corpus luteum during pregnancy
There are not many pathological conditions of VT, however, due to the disruption of progesterone synthesis, they have a significant impact on the ability to conceive a child and maintain a pregnancy.
Absence of corpus luteum
One of these conditions is the absence of the corpus luteum, which is manifested by the inability to get pregnant.
In the case when pregnancy is observed, but the luteal body cannot be visualized during ultrasound examination, several reasons can be assumed:
- the temporary gland is less than 10 mm in size, which indicates a threat of interruption and the need for hormone replacement therapy;
- anatomical feature of the location of the ovary;
- consequences of pathological processes suffered previously (for example, adhesions after an inflammatory disease);
- physiological characteristics of a woman’s body during pregnancy (many women indicate increased gas formation);
- impossibility of performing transvaginal ultrasound;
- insufficient qualification of a specialist.
Hypofunction
This is a pathological condition characterized by insufficient production of progesterone. This deficiency leads to miscarriage in early pregnancy.
Functional deficiency can be suspected if the corpus luteum on ultrasound is determined to be smaller in size than it should be normally. When an ultrasound doctor suspects hypofunction of the corpus luteum, the patient is sent for a blood test to determine the level of progesterone. Thanks to the achievements of modern medicine and pharmacology, insufficient amounts of the hormone can be replenished by taking medications prescribed by the gynecologist.
Corpus luteum cyst
A cystic formation is a small “bubble” with liquid contents, which on ultrasound is identified as a black, often round, inclusion.
If a cyst is suspected on ultrasound, the corpus luteum will be larger than 35-40 mm in size. The cyst does not affect the ability of the gland to secrete a sufficient amount of progesterone. But if it is large enough, it can rupture, which can lead to bleeding, and this is a surgical pathology. Emergency conditions requiring surgical treatment also include torsion of the cyst stalk.
The conclusion “corpus luteum cyst” on ultrasound without clinical manifestations is not an indication for any treatment. By the time the placenta is formed and the corpus luteum undergoes reverse development, the cyst will also go away.
You should immediately consult a doctor if a cyst has previously been identified and the following suddenly arise:
- lower abdominal pain;
- decreased blood pressure;
- loss of consciousness.
Such complications can be avoided if you follow your doctor's recommendations to avoid physical activity and limit sexual contact.
Why study the condition of the gland?
The maximum size of the corpus luteum reaches 26 mm. Just emerging, it measures 12 mm. Height depends on the period of the menstrual cycle. If its parameters do not meet the standards, doctors suspect pathology.
The corpus luteum does not attract attention if the woman is healthy and has no pathologies of the reproductive system. Normally, an ultrasound shows a small round sac in the ovary, that is, the temporary gland itself, the parameters of which correspond to the norm.
Indications for monitoring the state of this temporary formation and the process of its origin and development are:
- suspicion of infertility;
- diagnostics of the endocrine system;
- pregnancy planning;
- early stages of pregnancy;
- suspicion of follicular cyst or corpus luteum cyst.
If a woman is suspected of having any pathologies, such as lush or loose endometrium, which is not typical for the non-pregnant state of the uterus, she is prescribed an ultrasound diagnosis of the ovaries.
Assessing whether this element of the reproductive system is working well enough is done by monitoring basal temperature over a long period. Additionally, to study the functioning of VT, a blood test for progesterone and a biopsy of the uterine endometrium are prescribed.
