Genetics Northern California

Quad Marker Screening

Quad Marker Screening is a voluntary prenatal test available to pregnant women who start prenatal care after the 14th week in pregnancy but before the 20th week. This screening test is part of the California Prenatal Screening Program. The goal of the Prenatal Screening Program is to offer all pregnant women in California the option to be screened for certain birth defects during pregnancy.  You can choose whether or not you want prenatal screening during your pregnancy.

It is important to know that this test does not look for all types of birth defects. Below is a list of the conditions included in the California Prenatal Screening Program:

Quad Marker Screening is a single blood test done between 15 weeks to 20 weeks in pregnancy. This blood test measures four substances naturally found in a pregnant woman's blood including: alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), unconjugated estriol (uE3), and inhibin-A (INH). These are made by the placenta and the fetus (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 based on your blood test values and your age, and is usually available about one to two weeks after your blood is drawn. An estimated risk for each birth defect being screened is included in the result. The result is called "Screen Negative" when all of the risks are lower than the State cut-offs. If any of the estimated risks are higher than the State cut-offs, the result is called "Screen Positive", and 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.  
For more information about the California Prenatal Screening Program go to their website: Prenatal Screening Program

Last reviewed: December 1, 2017
Reviewed by: Kimberly Barr, MS, LCGC