ESTRIOL(E3) Detail

The Estriol (E3) test measures the level of estriol, a type of estrogen produced in significant amounts only during pregnancy. Estriol is made by the placenta and the fetal liver, and its levels rise steadily throughout pregnancy. It is the least potent of the three main estrogens (estradiol, estrone, and estriol), but it is vital for monitoring fetal development and placental function.

This test is commonly included in the second-trimester triple or quadruple screening to assess the risk of fetal abnormalities, such as Down syndrome and neural tube defects. Low levels of estriol in pregnancy may indicate chromosomal abnormalities or placental insufficiency.

Outside of pregnancy, estriol levels are typically low and not commonly measured.

Clinical Indications:

• Monitoring fetal development during pregnancy

• Part of second-trimester prenatal screening (triple/quadruple marker test)

• Evaluation of placental health and function

• Assessment of risk for congenital abnormalities