AFP4 (Quad Marker) Screening
AFP4 (Quad Marker) screening is an optional blood test done between 15 weeks to 21 weeks in pregnancy. This test may be offered when cell-free DNA screening cannot be done. The test looks for certain birth defects during pregnancy. The choice to have this test is up to you.
Below is a list of the conditions AFP4 can help detect:
- Down syndrome
- Trisomy 18
- Neural Tube Defects (anencephaly and spina bifida)
- Abdominal Wall Defects (gastroschisis and omphalocele)
AFP4 measures four substances found in your blood when you are pregnant: alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), unconjugated estriol (uE3), and inhibin-A (INH). These are made by the placenta and the developing baby. The chance for birth defects is estimated based on your blood test values and your age.
The amount of each substance can be affected by many factors including:
- Your gestational age (how far along you are in the pregnancy)
- Your weight
- Your race (ethnicity or ancestry)
- Whether you have diabetes
- Whether you have a single fetus or twins
- Whether you have smoked one or more cigarettes in the week prior to having your blood test.
AFP4 Test Results
Your result is available about one to two weeks after your blood is drawn.
Most results are "Screen Negative". This means the chance is low for the baby to have any of the birth defects the test looks for and no follow-up is needed.
When the result is "Screen Positive", the chance for a birth defect is high enough to offer follow-up services. This could include genetic counseling, detailed ultrasound, and amniocentesis.
Last reviewed: September 21, 2022
Reviewed by: Kimberly Barr, MS, LCGC