Free estriol in serum

Estriol - the main steroid hormone, synthesized by the placenta. In the first stage of the synthesis, which takes place in the embryo, the cholesterol produced de novo or coming from the pregnant woman's blood turns into pregnenolone, which is sulfated by the adrenal cortex of the fetus in DHEA, then in the fetal liver is converted to α-hydroxy-DHEA, and then to estriol in placenta. As a rule, the content of estriol in the pregnant woman's blood is correlated with the activity of the adrenal glands of the fetus. Estriol penetrates into the bloodstream of a pregnant woman, where it is possible to determine the concentration of its unconjugated form.

In pathology (pronounced malformations of the central nervous system in the fetus, congenital heart disease, Down syndrome, fetal growth retardation, fetal adrenal hypoplasia, intrauterine fetal death), the concentration of free estriol in the serum of the pregnant woman decreases.

With Down's syndrome and Edwards, the concentration of free estriol is usually 0.7MoM.

Concentration of estriol in serum in the dynamics of physiological pregnancy

Pregnancy, ned	Median, nmol / l	Reference values, nmol / l
6-7	1.2	0.6-2.5
8-9	1.6	0.8-3.5
10-12	4	2.3-8.5
13-14	8	5,7-15
15-16	10	5.4-21
17-18	12	6.6-25
19-20	15	7,5-28
21-22	24	12-41
23-24	28	18.2-51
25-26	31	20-60
27-28	32	21-63.5
29-30	35	20-68
31-32	38	19.5-70
33-34	43	23-81
35-36	52	25-101
37-38	64	30-112
39-40	65	35-111

Median concentrations of free estriol in serum for screening of congenital malformations in the second trimester of pregnancy

Gestational age	Medians for free estriol, nmol / l
15	4.3
16	4.8
17th	5.5
18	6.4
19	7.1
20	8.2

[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11]