Description
Why It’s Done
This test is mainly done during pregnancy to:
• Evaluate fetal health and development, especially in the second trimester (usually between 15–20 weeks).
• Screen for chromosomal abnormalities, such as Down syndrome (trisomy 21) and Edwards syndrome (trisomy 18) when used in combination with other markers (like AFP and hCG).
• Assess placental function, as estriol is produced by both the fetus and placenta.
Low levels of unconjugated estriol may indicate a higher risk of genetic or developmental issues, but abnormal results do not confirm a diagnosis—further testing is typically required.
Preparation
• No special preparation is generally needed.
• Inform your doctor of any medications you are taking, especially steroids or hormone-based treatments, as they may affect the results.
• The test is done via a blood sample from a vein, typically in the arm.
• It is important to know gestational age, as estriol levels vary throughout pregnancy and accurate interpretation depends on it.
