Free estriol during pregnancy - features, norms and interpretation

With the onset of pregnancy, a woman is faced with a very large amount of information new to her. This applies, first of all, to her changed hormonal background. To control it, a woman must take appropriate tests. One of the hormones to be observed is free estriol.

Hormone estriol: what is it?

Estriol is a hormone that predominates primarily in women. However, it can also occur in men, but in negligible amounts. Therefore, scientists attribute this hormone to a number of women. It belongs to the group of estrogens that express increased activity in the second half of pregnancy, replacing progesterone.

Until conception in a woman’s body, free estriol is inactive and predominates in small quantities. But after pregnancy, its role increases significantly. Along with progesterone, it has a supportive effect for bearing a child. That is why you need to constantly monitor its concentration in the body of a woman.

Any fluctuation in the hormone content may indicate possible pathologies of the development of the fetus. By passing special tests, you can determine, for example, placental insufficiency, a frozen pregnancy or premature detachment of the placenta. This allows you to take appropriate action as early as possible.

What is estriol for?

This hormone is an important diagnostic characteristic for the utero-placental communication between the mother and the baby. It is formed as a result of cholesterol entering the adrenal glands and the liver of a child. In the process of complex biochemical transformations, the final product - estriol - penetrates the placenta. The further pathway of the hormone passes through the mother’s circulatory system, then enters the liver, where it is processed and excreted in the urine.

The norm of free estriol performs the following functions during the bearing of a child:

• affects the growth and formation of the uterine cavity;
• enhances energy metabolism;
• controls the production of enzymes and processes in the uterus;
• affects the uteroplacental blood flow;
• prepares the breast for the process of feeding the baby.

Estriol concentration study

In order to monitor the concentration of the hormone, it is necessary to take an analysis for free estriol. This study relates to an enzyme-linked immunosorbent assay in serum. You can do it in any laboratory that can provide you with this type of diagnosis. The direction for this study is prescribed by a gynecologist, in whom a pregnant woman is registered. However, you can check the content of the hormone in the blood without direction, you just need to know the name of the hormone being studied. The analysis is carried out mainly during the second screening, approximately for a period of 16-17 weeks.

In diagnostic medicine, the analysis for this hormone is referred to as EZ. The units of free estriol are ng / ml or nmol / L. For such an analysis, venous blood is taken. You can get the result of the diagnosis the very next day.

Risk groups

There are certain factors, the presence of which requires more careful monitoring of the content of free estriol in women in position. Among them:

• blood relationship of parents;
• if future parents are older than 35-45 years old;
• the presence of genetic pathologies in the genus;
• if miscarriages, abortions, missed pregnancies were previously observed;
• the impact on parents of negative environmental factors (e.g. chemicals);
• hypertension or diabetes in a pregnant woman;
• future mother consumes drugs hazardous to the fetus;
• the presence of fetal development pathologies;
• difficult pregnancy;
• rhesus conflict.

How to prepare for the analysis?

In order for the indicator of unconjugated (free) estriol to be the most reliable, some requirements must be observed before the study. Namely:

• refuse fatty, salty, smoked or spicy foods;
• to exclude the use of alcohol (which is unacceptable for a woman in a position);
• the best option is to take an analysis on an empty stomach;
• half an hour before the test, you need to calm down, relax and in no case do not smoke;
• if you are taking any medications, especially hormones, then you need to inform the diagnostician about this, as this may affect the result of the analysis.

Decryption analysis

It is better to interpret the results at a doctor's appointment. Having misunderstood any indicator, you can deliver yourself unnecessary excitement and anxiety.

However, if you decide to check the free estriol indicator during pregnancy yourself, without a doctor’s direction, you need to understand yourself whether you normally have a hormone or not. For this, clinicians have created a table in which the norms for each stage of pregnancy are indicated.

The norm of free estriol during pregnancy

As we already mentioned, the indicator of this hormone will vary depending on the gestational age.

It is necessary to check the concentration and volume of the hormone in the blood at the same time, since the situation may change at different times of the day. The hormone reaches its highest concentration at 14-15 hours of the day, so it is better to take an analysis on an empty stomach in the morning.

In the case when the level of free estriol corresponds to the norm (you can see in the table above), then nothing threatens your pregnancy, and it develops normally. But if it is reduced or, conversely, increased, an additional examination should be performed to identify pregnancy pathology.

Deviations from the norm

An increased level of estriol can symbolize a multiple pregnancy, a large fetus, or a fetal abnormality in the liver. This indicator is not found as often as low estriol.

If the indicator is reduced by 40% of the norm, then this may mean:

• risk of overexposure;
• the presence of chromosomal abnormalities such as Down syndrome, Patau or Edwards;
• the threat of spontaneous abortion;
• the presence of intrauterine infection;
• fetoplacental insufficiency;
• the formation of cystic drift, etc.

However, it should also be borne in mind that low free estriol may be due to the use of antibiotics or hormonal drugs.

Triple screening test

As we wrote above, analysis for unconjugated estriol is one of the mandatory studies during the second screening, which is carried out within 14-20 weeks.

Triple screening test involves taking a woman’s blood in a position for analysis on the level of hCG, AFP and free estriol. This study allows you to calculate the risk of developing chromosomal diseases in the fetus, CMD and the risk of delayed fetal development. Let's analyze this test into its components.

HCG (human chorionic gonadotropin) is a placental protein that begins to be produced immediately after implantation of a fetal egg in the uterus (approximately 4-5 days after fertilization). By the presence of this protein, one can understand whether pregnancy has occurred or not. In the blood, this protein appears earlier than in the urine, therefore, if you want to know about the onset of pregnancy as soon as possible, you can take an analysis for this hormone in any diagnostic laboratory.

Decreased hCG may mean antenatal fetal death, risk of spontaneous abortion, placental insufficiency, or excess gestational age.

Increased hCG indicates a multiple pregnancy, mismatch of pregnancy, toxicosis, gestosis or the presence of diabetes in a pregnant woman.

AFP (alpha-fetoprotein) - also applies to proteins. It is produced by the baby’s liver and enters the mother’s circulatory system. Diagnosis of the level of this protein is necessary for the timely detection of defects in the fetus of the nervous system, digestive and urinary systems, Shershevsky-Turner and Down syndromes, lagging in the development of the child or impaired functioning of the placenta.

A reduced AFP level may symbolize Down syndrome, low placentation, the presence of diabetes in the future mother or hypothyroidism.

An overestimated AFP level means anomalies in the development of the nervous system (pathology of the spinal cord, underdevelopment of the brain and its parts), which are fraught with the birth of a child with cerebral palsy or mental retardation, due to anomalies in the structure of the brain (anencephaly, macrocephaly, microcephaly, hydrocephalus, etc.) . There is also a risk of an unfavorable course of pregnancy, the threat of spontaneous abortion, oligohydramnios or a missed pregnancy. With multiple pregnancies, a high AFP level is the norm!

E3 (free estriol) is a hormone produced by the placenta and fetal liver. It is necessary to assess the condition of the uteroplacental circulatory system between the mother and the fetus.

Low EZ is the threat of miscarriage, prematurity or prolongation, FPI, malnutrition or anemia in the fetus, intrauterine infection.

High EZ is a large fetus or multiple pregnancy, the presence of kidney and liver diseases in the fetus. If the hormone rises too sharply, it may mean a risk of premature birth.

A change in one of the indicators has no diagnostic value. For a more complete analysis of the situation, programs are used that calculate the risks, taking into account the individual parameters of each pregnant woman.