Estriol (Unconjugated) E3 Test

The test is primarily used as a marker of the health of the growing baby in the mother’s womb. Since E3 originates from the foetus, it is an excellent way to determine the development of the baby. Your doctor may order the E3 test for the following reasons:

• Routine second-trimester testing: Unconjugated E3 test is a part of the routine tests performed on the mother’s blood to assess the progress of the pregnancy 
• Monitoring a high-risk pregnancy: If your doctor suspects that there are certain risks associated with your pregnancy, he/she may order this test serially for several days to check for a rise or fall in the E3 levels over time.
• As part of the triple marker test: E3 test is a part of the triple marker test which also checks for the levels of alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG) in the mother’s blood. It is a screening test, which helps the doctor assess the chances of genetic disorders in the baby. Your doctor may request the triple marker test in the following scenarios:
  • If you are above 35 years of age
  • If you have a family history of congenital anomalies 
  • If you have diabetes and are on insulin therapy
  • If you have been exposed to harmful medications or radiation during pregnancy
  • If you had a viral infection during pregnancy

You do not require any preparation before this test. Since E3 levels can vary through the day, it is essential that the test is performed at the same time each day when ordered serially. It is also crucial that you discuss all your health details with your doctor. These include:

• The week of pregnancy you are in 
• If you have conditions like anaemia, kidney disease or liver disease 
• If you are taking any health supplements or medicines

The test is performed on a small sample of the mother’s blood. Collecting a blood sample usually takes only five to 10 minutes. A laboratory technician or nurse will use a sterile needle to draw a blood sample from a vein in your arm. The blood sample will then be transferred into a special container, labelled with your details and sent to the laboratory for testing. 

You may experience mild pain or discomfort from the needle, but this will subside soon. Some people tend to experience slight bruising at the site of needle insertion, which usually fades away in a few days. In case the bruise persists, please inform your doctor.

Normal results:

E3 level in maternal blood increases as the pregnancy progresses. Table 1 lists a reference range of values for the second trimester. The values for the third trimester are usually five to 10 times higher than those for the second trimester. 

Table 1: Values of unconjugated E3 during the second trimester

Normal values for E3 may vary from one laboratory to another.

Abnormal results:

An E3 level below or beyond the normal values is considered abnormal. Lower than normal values of E3 in the maternal blood could indicate one of the following conditions in the baby:

• Down syndrome
• Abnormalities in the development of the adrenal gland
• Defects in the development of the neural tube (which gives rise to the nervous system)
• Smith–Lemli–Opitz syndrome (a rare condition where the body may not be able to form the precursors for E3)
• Placental sulfatase deficiency (another rare condition where the correct form of E3 is unable to reach the placenta)

Higher than normal values of E3 could be an indicator of impending labour or multiple pregnancies, meaning that someone is carrying more than one baby. (Read more: Natural birth vs C-section)

Please discuss the details of your test results with your doctor. 

E3 test is not diagnostic for a specific condition but helps to screen for potential risks in pregnancy. Your doctor will interpret the results based on your age, weight, weeks of pregnancy and the results of other tests, such as AFP and hCG. Depending on the results, he/she may order further tests to make a diagnosis.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.