The triple marker screen test is also known as the triple test, multiple marker test, multiple marker screening, and AFP Plus. It analyzes how likely an unborn baby is to have certain genetic disorders. The exam measures the levels of three important substances in the placenta:
- alpha-fetoprotein (AFP)
- human chorionic gonadotropin (HCG)
Triple marker screening is administered as a blood test. It’s used for women who are between 15 and 20 weeks pregnant. An alternative to this test is the quadruple marker screen test, which also looks at a substance called inhibin A.
A triple marker screen test takes a sample of blood and detects the levels of AFP, HCG, and estriol in it.
AFP: A protein produced by the fetus. High levels of this protein can indicate certain potential defects, such as neural tube defects or failure of the fetus’s abdomen to close.
HGC: A hormone produced by the placenta. Low levels may indicate potential problems with the pregnancy, including possible miscarriage or ectopic pregnancy. High levels of HGC can indicate a molar pregnancy, or a multiple pregnancy with two or more children.
Estriol: An estrogen that comes from both the fetus and the placenta. Low estriol levels may indicate risk of having a baby with Down syndrome, especially when paired with low AFP levels and high HGC levels.
Abnormal levels of these substances may indicate the presence of:
- neural tube defects, such as spina bifida and anencephaly
- multiple infants, such as twins or triplets
- an improper timeline, where the pregnancy is further along or not as far along as once thought
Abnormal levels can also indicate Down syndrome or Edwards syndrome. Down syndrome occurs when the fetus develops an extra copy of chromosome 21. It can cause medical problems and, in some cases, learning disabilities. Edwards syndrome can result in extensive medical complications. These are sometimes life-threatening in the first months and years after birth. Only 50 percent of fetuses with this condition survive to birth, according to the Trisomy 18 Foundation.
Triple marker screen tests help prospective parents prepare and assess options. They also alert doctors to watch a fetus more closely for other signs of complications.
The test is often most recommended for women who:
- are 35 years old or older
- have a family history of birth defects
- have diabetes and use insulin
- have been exposed to high levels of radiation
- had a viral infection during pregnancy
Preparation and risk
Women do not need to prepare for a triple marker screen test. There are no eating or drinking requirements beforehand.
Moreover, there are no risks associated with taking the triple marker screen test.
The triple marker screen test is administrated in a hospital, clinic, doctor's office, or lab. The process is similar to any other blood test.
A doctor, nurse, or lab technician cleans the patch of skin where they will insert the needle. They will likely place a rubber band or other tightening device on your arm to make a vein more accessible. The health professional then inserts the needle to draw blood, and they remove it when the vial is full. They clean the site of injection with a cotton swab or other absorbent material and put a bandage on the wound.
The blood is then sent to a lab for assessment.
There are no side effects for triple marker screen tests. You may experience slight discomfort due to the needle used to take blood, but that fades quickly.
A triple marker screen test can indicate potential complications with a pregnancy, as well as the presence of multiple fetuses. This helps parents prepare for birth. If all the test results are normal, parents know that they are less likely to have a child with a genetic disorder.
The results of the triple marker screen test show the likelihood of an infant having a genetic disorder such as Down syndrome or spina bifida. Test results aren’t infallible. They merely show a probability, and may be an indication for additional testing.
Doctors often consider several other factors that can affect the test results. These include:
- the mother’s weight
- her ethnicity
- her age
- whether or not she has diabetes
- how far along the she is in her pregnancy
- whether or not she’s having a multiple pregnancy
Parents who receive negative indicators on their triple marker screen test must then decide what actions to take. While abnormal results can be concerning, they don’t necessarily mean that there’s anything to worry about yet. Instead, they’re a good indication to explore further testing or monitoring.
In the case of abnormal results, an amniocentesis test may be ordered. In this test, a sample of amniotic fluid is taken from the uterus via a thin, hollow needle. This test can help detect genetic conditions and fetal infections.
If your results show high levels of AFP, your doctor will likely order a detailed ultrasound to examine the fetal skull and spine for neural tube defects.
Ultrasounds can also help determine the age of the fetus and how many fetuses a woman is carrying.