Estriol (E3) blood test
Quick answer: An estriol test measures a form of oestrogen made mainly by the placenta and baby during pregnancy. It is mainly used as part of second-trimester screening tests such as the triple or quadruple marker.
- SampleBlood
- TakesAbout 5 minutes
- Before the testNo special preparation is usually needed.
- In fertility careEstriol is part of second-trimester screening for chromosomal conditions in the baby.
How the test is done
- 1You share your scan report so the exact week of pregnancy is known
- 2A needle draws blood from a vein
- 3The lab measures unconjugated estriol
- 4It is combined with other markers to calculate a screening chance
What your results can mean
Reading your report
The result is read against the exact week of pregnancy, so discuss it with your doctor.
If the result is outside the usual range
In pregnancy, a low level can be seen with a higher chance of some chromosomal conditions, problems with the placenta or a wrong pregnancy date. The result is a screening chance, not a diagnosis.
Who usually has this test
Pregnant women in the second trimester, usually around 15 to 20 weeks, having triple or quadruple marker screening.
Risks and aftercare
There is no risk to the baby from this blood test; a small bruise may appear.
Names and options
Also called: E3, unconjugated estriol
Listed by the hospital as
- ESTRIOL (E3), SERUM
Questions about this test
Why is estriol part of the quadruple marker test?
Estriol is made by the baby and placenta. Combined with AFP, hCG and inhibin A, it helps estimate the chance of some chromosomal conditions.
What should I do if my screening result shows a higher chance?
Your doctor will explain your options, which may include a detailed scan, a cell-free DNA test or a diagnostic test such as amniocentesis.
Does the exact week of pregnancy matter?
Yes. Estriol changes with each week, so the lab needs your scan dating to read it correctly.
Related tests
Tamara Hospital & IVF Centre, Rajajinagar
34/3, 10th Cross Road, opp. Vardhaka Sardar Patel School, 1st N Block, 2nd Stage, Rajajinagar, Bengaluru 560010
The hospital is open 24 hours. Call before you come to check the timing for your scan or sample collection.
Get directions ↗IVF Pulse fertility care at Tamara Hospital →
Reception
Waiting area
IVF lab
This page explains each test in general terms so you know what to expect. It is not medical advice: your doctor decides which tests you need and what your results mean. Reference ranges differ between laboratories. Updated 4 November 2026.