Estriol (E3) Blood Test

What is the purpose of this test?

Order this Estriol (E3) Blood Test to measure the E3 hormone levels to help diagnose congenital disabilities and monitor a high-risk pregnancy. Estrogens are a group of hormones essential to developing female physical features and reproductive functions, such as:

• Growth of breasts, uterus, and reproductive organs
• Regulation of the menstrual cycle

Individuals should note that men also make estrogen but in much smaller amounts. Three main types of estrogens that are commonly tested include estrone (E1), estradiol (E2), and estriol (E3). E1 is the primary estrogen women produce after menopause, and E3 is the form of estrogen produced during pregnancy. This Estriol Blood Test measures the hormone commonly referred to as E3, which is the primary form of (estrogen) that pregnant women make. 

Estriol (E3) is produced by the placenta, with concentrations increasing throughout the pregnancy. Increasing levels indicate the pregnancy's overall health and the baby's development. In addition, it is usually performed during the second-trimester to assess fetal risk due to specific chromosomal abnormalities (congenital disabilities). Deficient levels of E3 are present in non-pregnant women or men.

What conditions cause abnormal estriol levels?

Several conditions may affect E3 levels, so discussing concerns with a healthcare provider and using blood tests such as this to help monitor hormone levels is essential. Estriol levels may be abnormally high due to conditions such as:

• The mother is over 35 years old during the pregnancy
• The mother is taking insulin to treat diabetes
• A family history of congenital disabilities

When should I order an Estriol Blood Test?

Individuals may order an Estriol Blood Test when:

• During pregnancy, a healthcare provider may request a series of E3 samples to assess whether there is an increase or decrease in the E3 level over time.
• Unconjugated E3 is often measured in the second-trimester of pregnancy as part of the triple/quad screen. Usually, to help diagnose any congenital disabilities or monitor a high-risk pregnancy.