What is the triple test in pregnancy?
The triple test is a maternal blood investigation performed during pregnancy to check for three specific substances: AFP, hCG and estradiol.
- AFP (alpha-fetoprotein) is a type of protein produced by the fetus.
- hCG (human chorionic gonadotropin) is a hormone produced by the placenta.
- Estradiol is an estrogen (female sex hormone) produced by both placenta and fetus.
The results of this test help identify the risk of certain birth defects.
Why Triple test is called as a triple screen test?
This test does not diagnose a defect, but only indicates the probability of having a defect. If the results of the triple test are abnormal that doesn't confirm that the baby has birth defects. The triple test result interpretation is done in comparison to various factors including age of mother, ethnicity, family history, etc. After comparing all the factors, the doctor estimates the chances of the baby having birth defects.
Triple test: How it is done
Blood samples are collected from the expecting mother between 16th and 18th week of pregnancy. It can also be performed between 15th and 22nd week. The samples are then sent to the laboratory for testing.
This test is recommended for all pregnant woman; however, the triple test high risk group includes the following:
- Age: 35 years or older
- Women with a family history of birth defects
- Women with diabetes and using insulin
- Women who have had a viral infection during pregnancy
- Women who may have been exposed to harmful medications during pregnancy
- Women who have been exposed to high levels of radiation during pregnancy
What is the aim of conducting the triple screen test?
The primary aim of the triple screen test is to look for possible genetic disorders; however, these values also help in identifying multiple pregnancies and the exact week of the pregnancy.
Blood test results may indicate high or low levels of AFP, hCG and estradiol. These values are evaluated in comparison to the mother's age, weight, weeks of pregnancy, and family history in order to assess possibilities of potential genetic disorders or birth defects.
If AFP levels are high, it suggests that the developing baby has neural tube defects such as spina bifida or anencephaly. However, often a high level of AFP is also due to inaccurate dating of pregnancy.
If AFP levels are low and hCG and estradiol levels are abnormal too, this suggests that the developing baby has Down Syndrome (Trisomy 21), Edwards Syndrome (Trisomy 18) or another type of chromosomal abnormality.
What if the triple test results are abnormal?
As mentioned earlier, this is just a screen test and not a diagnostic test. It is also known to have high chances of false positives, mostly because of incorrect calculation of the duration of pregnancy by the doctor. If values are abnormal, your doctor will order further testing for accurate diagnosis.
Often, the first step is to undergo an ultrasound scan. An ultrasound will help in checking the age of the baby and analyzing the spinal cord, brain, kidneys, and heart for possible birth defects.
If the ultrasound examination also provides abnormal results, another test that is recommended; it is a more invasive procedure called as amniocentesis. It helps in checking the fluid directly around the baby. Combining results of all these tests will help the doctor to analyze if the developing baby has any serious birth defects.
It is often seen that some couples are skeptical to perform these tests due to various personal reasons. However, the doctor’s advice should always be followed if the test has been advised to you. Your doctor will discuss the risks and benefits of all the tests before doing the procedure.
Disclaimer: The information in the article is not intended or implied to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your doctor.