Genetics Northern California

Quad Marker Screening

Quad Marker Screening is an optional test for pregnant women who start prenatal care between 15 weeks to 20 weeks in pregnancy. This test is part of the California Prenatal Screening Program. The Prenatal Screening Program test is offered to all pregnant women in California. The test helps detect some birth defects during pregnancy. The choice to have this test is up to you. 

This test does not look for all birth defects. Below is a list of the conditions the test can help detect:

Blood Test 2Quad Marker Screening is a single blood test done between 15 weeks to 20 weeks in pregnancy. This test measures four substances naturally found in a pregnant woman's blood: 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 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.  

Quad Marker Screening Test Results

Your result is available about one to two weeks after your blood is drawn. The chance for birth defects is estimated based on your blood test values and your age.  Most results are "Screen Negative". That means the risk for birth defects is lower than the State cut-offs. When the risks are higher than the State cut-offs, the result is called "Screen Positive". Follow-up services are offered, including genetic counseling, detailed ultrasound, and amniocentesis.

Screen Negative Result
A screen negative result means that the chance for Down syndrome, neural tube defects, abdominal wall defects, trisomy 18, and SLOS is low enough that follow-up testing is not routinely offered. Up to 95% of women will have a screen negative result. It is important to remember that a screening test will not tell for certain whether the baby actually has a birth defect, but instead tells the chance of a specific problem occurring. Some women whose babies actually have one of the birth defects included in the California Prenatal Screening Program will be missed with the screening test.

Screen Positive Result
A screen positive result means that there is a higher chance for certain birth defects in your pregnancy, such as Down syndrome, neural tube defects, abdominal wall defects, trisomy 18 or SLOS. Most of the time, however, the reason for the screen positive result is NOT a birth defect. The most common reason for this type of result is normal variation. In other words, the amounts of the substances are different than average, but normal for your baby.

Kaiser Permanente members with screen positive results can have genetic counseling and follow-up services at any Kaiser Permanente Genetics Department or any of the State-approved Prenatal Diagnosis Centers.  There is no co-pay or additional fee for these follow-up services.  
Click here for more information about the California Prenatal Screening Program go to their website.

Last reviewed: March 11, 2021
Reviewed by: Kimberly Barr, MS, LCGC