What is Estriol?

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  • Written By: Mary McMahon
  • Edited By: O. Wallace
  • Last Modified Date: 11 September 2019
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Estriol is a natural estrogen which is associated with pregnancy. In pregnant women, estriol is produced in the fetus by the fetal liver and in the placenta. Levels of estriol in the blood and urine can be used to determine whether or not a woman is pregnant, and to monitor the progress of the pregnancy. Abnormal estriol levels can indicate that there is a problem with the developing fetus which could bear closer monitoring or additional testing. The quad screen routinely recommended to pregnant women includes a check on estriol levels.

Two other natural estrogens are found in the body: estradiol and estrone. While many people think of estrogens as female hormones, they are also present in men, and they play an important role in fetal development, whether a child is male or female. Estrogens are produced from androgens, hormones which are associated with masculine traits, through the action of various enzymes in the body.

Estriol levels are typically highest in women of childbearing age, and they increase during pregnancy. Otherwise, estriol levels in women and men are fairly similar, unless estriol is being taken as a supplement. This hormone is sometimes used to manage the symptoms of menopause, and it has been used in the treatment of some other conditions as well. Levels of estriol in women taking supplements can be very high.


This estrogen is much weaker than the other natural estrogens found in the body. Also known as theelol, this hormone is a topic of interest among researchers who want to learn more about the role of hormones in the body, and the role of hormones at various life stages. It can be produced synthetically in addition to being derived from animal sources for therapeutic use.

If a quad screen reveals abnormalities in estriol levels, this is not necessarily a cause for panic. Quad screens can be imprecise, and the abnormal levels may be nothing to worry about. The only way to determine whether or not abnormalities on a quad screen are a cause for concern is to undergo additional testing to learn more about the situation. As with any kind of health screen, it is a good idea to talk with a doctor before the test is performed to learn more about what the lab will be looking for, possible results, and the implications of those results. Being prepared ahead of time can make the experience less stressful.


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Post 2

@SailoryJerry - Congrats on the coming baby!

It's important to understand the difference between a screening test and a diagnostic test. The quad screen is a screening test; it is used to refer people for further testing.

Now, the further testing can be dangerous. Amnio and CVS (which is done earlier) do have a chance of causing miscarriage and CVS can also cause limb abnormalities. So before you decide whether to have the quad screen, ask yourself if you would pursue further testing. Maybe you and your wife are young and would have plenty of time to try again, but feel that you would have a lot of difficulty caring for a child with special needs. In that scenario

, the quad screen makes sense because you would likely be willing to pursue the amnio.

On the other hand, if you had a lot of trouble conceiving and don't want to do anything to jeopardize the pregnancy, then you might as well skip the quad screen because you wouldn't have an amnio or CVS anyway. You could consider more informative non-invasive tests, like a level II ultrasound.

Post 1

How can my wife and I decide whether or not to have the quad screen? I hear that it has a really high false positive rate and I don't want us to be worried unnecessarily, but of course if our baby has a problem, I want to know about it so we can make the best decisions for us.

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