One of the causes that prevent pregnancy is thin endometrium. Such condition occurs when the endometrium (tissue that lines the uterus internally) has a reduced thickness, which makes it impossible to attach the embryo to the uterine wall and support the fetus during pregnancy. Thus, the endometrium cannot reach at least 7 mm of thickness on ultrasound. This condition affects about 2.5% ofWhen the endometrium does not grow properly, it may not develop the changes that make it receptive to pregnancy, so the embryo cannot implant.

However, some specialists consider that more important than the thickness of the endometrium, is its aspect. A favorable endometrium has a trilaminar aspect on the ultrasound (with three slides). Thus, an endometrium smaller than 7mm, with trilaminar aspect, can be receptive. It is important to emphasize that pregnancies occur with thin endometriums of up to 4 or 5mm, however, when we analyze thestatistics, the chances of pregnancy in these cases are lower.

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Flexible endometrium

To understand the importance of the thickness of the endometrium, we need to understand its physiology. During menstruation, the endometrium flakes off and becomes thin (less than 5mm thick). However, throughout the menstrual cycle, the hormone estradiol produced by the ovary begins to proliferate in the endometrium, making it progressively thicker until the moment of ovulation, when it reaches maximum thickness, which is,in general, between 7 and 14 mm.

After ovulation, the ovary starts producing another hormone: progesterone, which, among other functions, acts on the endometrium to stop it from growing, but increases the secretion of the glands and induces immunological and vascular changes to make the endometrium receptive to the embryo. In general, after 5 days of progesterone, the endometrium can already receive the embryo.

Symptoms of Thin Endometrium

Most women with thin endometrium are asymptomatic and only find out they have it by ultrasound. However, when endometrium is too thin, menstruation may come with less flow and fewer days of bleeding. Also, in extreme situations, it can stop menstruations, a condition also known as amenorrhea.

Causes of thin endometrium

The main causes of thin endometrium are infections and injuries from uterine procedures. It is worth pointing out that the endometrium has two layers: a deeper one (the basal layer), which never flakes off and is responsible for the regeneration of the endometrium after menstruation; and a more superficial one (the functional layer), which grows under hormonal stimulus and flakes off during menstruation.

When there is a lesion in the basal layer, the endometrium can no longer grow in that region. This can occur in inflammatory processes, such as infections (endometritis) and after uterine surgeries, such as the removal of fibroids and polyps, and especially after uterine curettage.

In these cases, the scars in the endometrium (synechiae) prevent its growth. In more severe cases, the entire endometrium can be affected, and is called Asherman's Syndrome, in which case the menstrual cycles are interrupted because the endometrium no longer grows.

Another common cause of thin endometrium is the use of progestogens (progesterone-like drugs) or hormonal changes that lead to an unexpected increase in progesterone. Finally, thin endometrium can also be a normal feature of the endometrium in some women.

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How to treat thin endometrium to get pregnant?

The first step is to diagnose the thin endometrium. Tests such as hysteroscopy (a camera is inserted into the uterus to see the cavity of the endometrium) may be needed. If there is scarring in the uterus (synechiae) that is preventing it from growing, surgery can be done to remove these synechiae. If there is no scarring, hormone tests are done to see the levels ofCases in which estradiol is too low and progesterone is too high indicate that the endometrium is not growing properly.

Finally, cases in which the endometrium has no lesions and has adequate levels of hormone levels may indicate that such a characteristic is intrinsic to that endometrium. In this case, some measures can be proposed to improve the thickness of the endometrium, such as increasing the dose of estradiol, as well as trying to improve the pelvic circulation, which improves the response of the endometrium to hormonal stimulation.Medications such as aspirin and vasodilators like pentoxifylline, tadalafil, and sildenafil may also be indicated for oral or vaginal use.

Other types of treatment

Endometrial injection of G-CSF (granulocyte colony-stimulating factor) and PRP (platelet-rich plasma) may also be indicated. The former is a drug normally used to stimulate the production of white blood cells and can stimulate endometrial growth and increase gavidez rates. PRP, on the other hand, is produced from the patient's own blood (bloodIt is believed that these injections can increase endometrial growth and improve pregnancy rates. However, these treatments are still considered experimental.

There is also the possibility of an exam to evaluate the receptivity of the endometrium (ERA exam). endometrial receptivitiy array ) to know if, even thin, the endometrium is receptive, although this is also an exam that is the target of many controversies. There are also in vitro fertilization treatments. In these cases, the endometrium is prepared artificially before transferring the embryo. For this, estradiol is used for 10 to 15 days for the endometrium to grow, which is accompanied by ultrasound. When itreaches more than 7 mm on ultrasound, progesterone is started for another 5 days and then the embryos are transferred.

Ultimately, many times the endometrium cannot actually grow, and in some cases the only option left is a uterus transplant. Thus, treating thin endometrium is challenging and should be evaluated on a case-by-case basis by a medical specialist.

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Source: Dr. Rogerio B.F Leão, specialist in Infertility at IPGO's Human Reproduction Center - CRM - 104.152 RQE - 38.912