Blood draw
Free Estriol (E3)
Free Estriol; relevant in pregnancy.
€ 32,00
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Hormones · Blood
Free estriol
A weak estrogen made during pregnancy through the placenta and the unborn child; not very informative outside pregnancy.
At a glance
- Measured in blood
- In 1 test panel
- No special preparation
Explanation
Free estriol: what is measured?
Estriol (E3) is one of the three estrogens, alongside estrone (E1) and estradiol (E2). During pregnancy, the adrenal glands and liver of the unborn child make a precursor, which the placenta converts into estriol. As a result, estriol in the pregnant woman's blood rises as the pregnancy progresses. Free estriol is the part that has not yet been linked by the liver for removal. Outside pregnancy, the amount of estriol is very low.
What can it detect?
- Cooperation between the placenta and the unborn child in making hormones, as part of pregnancy testing with other tests and ultrasound
- Rarely: a congenital deficiency of the enzyme steroid sulfatase in the child, which gives a very low estriol and goes together with scaly skin (ichthyosis)
Result
What does the result mean?
Free estriol too high
In pregnancy, free estriol normally rises with the length of the pregnancy; with twins or more the value is higher. A value higher than expected is often because the pregnancy is further along than thought. Outside pregnancy, a raised value is unusual and is often due to the use of estriol cream or tablets, or to interference in the measurement.
Free estriol too low
Outside pregnancy, a low or unmeasurable value is normal. In pregnancy, a lower value than expected can fit a pregnancy that is less far along than thought, use of corticosteroids by the pregnant woman, or reduced function of the placenta. Rarely: a congenital enzyme deficiency or another condition in the child. A single low value is not a diagnosis and, without ultrasound and other tests, says little about the health of the child.
After an abnormal result
An abnormal value during pregnancy is assessed by the midwife or gynecologist, together with the length of pregnancy, the growth of the child on the ultrasound and other results. Outside pregnancy, an abnormal value usually does not lead to follow-up tests.
Reliability
How reliable is the test?
Free estriol can only be interpreted if the exact length of pregnancy is known, usually from the dating scan, and together with other tests and ultrasound examinations. A single value has limited predictive value: many abnormal results have a harmless cause, such as a wrongly estimated length of pregnancy. The test is not a test for conditions in the unborn child; the NIPT and the 13-week and 20-week ultrasound scans of the national prenatal screening program are meant for that. Outside pregnancy the values are so low that a result means little.
What can affect the result?
- Length of pregnancy: the value rises week by week; an estimate that is a few weeks off gives a falsely high or low result.
- Twins or more, corticosteroids and products containing estriol change the value.
- Measurement methods differ from each other; results from different laboratories are hard to compare.
- Outside pregnancy the value is often below the detection limit.
Who it is for
Who is the test useful for?
Useful for
The result only says something during pregnancy, if the length of pregnancy is known and the value is assessed together with ultrasound and other tests within maternity care. For people who are not pregnant, the test adds nothing. If you are pregnant and want to know whether your child is healthy, the tests of the national prenatal screening program, arranged through the midwife or gynecologist, are more useful.
How common is it?
All pregnant women in the Netherlands are offered the NIPT and the 13-week and 20-week ultrasound scans through the national prenatal screening program. How often an abnormal free estriol occurs has not been recorded for the Netherlands. A congenital deficiency of steroid sulfatase is rare and occurs almost only in boys.
RIVM, prenatal screening program
Drawbacks and risks
- A single abnormal result during pregnancy can cause great worry about the child, while the cause is usually harmless, such as a wrongly estimated length of pregnancy.
- A normal result can give false reassurance; the value says little about conditions in the child.
Get tested
Free estriol: test panels
Free estriol is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
More about risks and results