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 provide an opportunity for all pregnant women in California to have screening for certain birth defects during the pregnancy. It is important to remember that this test cannot look for all types of birth defects.
Below is a list of the conditions included in the California Prenatal Screening Program:
- Down syndrome
- Trisomy 18
- Neural Tube Defects (anencephaly and spina bifida)
- Abdominal Wall Defects (gastroschisis and omphalocele)
- Smith-Lemli-Opitz syndrome (SLOS)
Quad Marker Screening is a blood test done from 15 weeks to 20 weeks in pregnancy. This blood test measures the levels of four substances naturally found in a pregnant woman's blood. These substances are: alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), unconjugated estriol (uE3), and inhibin-A (INH). These substances are made by the placenta and the fetus (developing baby).
The amount of each substance is 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 calculated based on the information from your blood test and your age. The result is usually available about one to two weeks after the blood test. The blood test result provides you with a risk estimate for each birth defect included in the screening test. If all of the risks are lower than the State cut-offs, your result is considered "Screen Negative". If any of the estimated risks are higher than the State cut-offs, your result is considered "Screen Positive", and follow-up services are offered, including genetic counseling, detailed ultrasound, and amniocentesis.
Screen Negative: 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: A screen positive result means that there is an increased 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.
The California Prenantal Screening Program provides handouts for all screen positive results: www.cdph.ca.gov/programs/pns/Pages/InformationforPatients
Kaiser members with screen positive results are eligible for genetic counseling and follow-up services at any Kaiser Permanente Genetics Department, or any of the State-approved Prenatal Diagnosis Centers. There is no additional fee for these follow-up services.
For more information about the California Prenatal Screening Program go to their website: www.cdph.ca.gov/programs/pns
Last reviewed: January 11, 2013
Reviewed by: Kaiser Permanente Genetics