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Unbound (free) estriol in the blood
Last reviewed: 14.07.2022
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Estriol is the main estrogen synthesized by the placenta during pregnancy. Unbound estriol passes through the placenta and enters the bloodstream of the pregnant woman, where it quickly turns into glucuronide and sulfate derivatives, which facilitates the process of its excretion. The half-life of estriol in the blood of a pregnant woman is only 20-30 minutes. In this regard, its definition - a convenient and fast way to assess the current state of the fetus. The concentration of estriol in the blood is constantly growing throughout pregnancy and especially rapidly in its last third (28-40 weeks).
Concentration of free estriol in the serum of pregnant women
|
Pregnancy, ned |
Estriol, ng / ml |
|
28-30 |
3.2-12 |
|
30-32 |
3.6-14 |
|
32-34 |
4.6-17 |
|
34-36 |
5.1-22 |
|
36-38 |
7.2-29 |
|
38-40 |
7.8-37 |
A sudden decrease in the production of estriol leads to a rapid drop in the concentration of its unbound fraction in the blood serum. The determination of unbound estriol has several advantages over the determination of its total fraction in serum or urine, since it does not depend on the presence of kidney or liver diseases and on the use of various antibiotics. The concentration of unbound estriol more accurately reflects the likely outcome of pregnancy in diabetic patients.
The concentration of estriol in body fluids is usually measured to determine fetal status, particularly in pregnant women with a high risk of premature birth or fetal death. Due to the fact that the ranges of normal concentration of unbound estriol in the blood serum are very wide, a single study is not enough. It is necessary to constantly monitor this indicator in order to establish the trend of its changes in each specific case. Constantly reduced concentration or its sudden and prolonged decline during the last third of pregnancy usually indicates a pathology of the fetus (including its intrauterine death).
Diseases and conditions in which the concentration of free estriol in the blood serum changes
|
Increase in concentration |
Reduction in concentration |
|
A sharp increase in the likelihood of premature birth |
In the pathology of pregnancy (pronounced malformations of the central nervous system in the fetus, congenital heart disease, Down's syndrome, fetal growth retardation, rhesus-conflict, fetal anemia, pyelonephritis, malnutrition, hemoglobinopathy, The use of penicillin |