Genetics Northern California

Serum Integrated Screening

Serum Integrated Screening is a voluntary prenatal test available to pregnant women who start prenatal care before the 14th week in pregnancy.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 remember 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:

Serum Integrated Screening includes two separate two blood tests.
Blood Test 1First trimester blood test (10 to 13 weeks): Serum Integrated Screening starts with a first trimester blood test that measures two substances in your blood: human chorionic gonadotropin (hCG) and pregnancy-associated plasma protein-A (PAPP-A). These substances are normally found in a woman's blood only during pregnancy. 
The first blood test is done by taking a small amount of blood from your arm between 10 weeks and 13 weeks 6 days in pregnancy.

Blood Test 2Second trimester blood test (15 to 20 weeks): The second part of Serum Integrated 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 found in the blood sample 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 one fetus or more (twins, triplets)
  • Whether you have smoked one or more cigarettes in the week prior to having either blood test


When are results available?
Serum Integrated Screening will give you results about one to two weeks after the second blood test. You will not get any result until the second blood test is completed.

What type of result is reported? 
The information from both blood tests is combined to estimate your risk for the selected birth defects. Results are reported as either Negative (low risk) or Positive (high risk). 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 the follow-up services.

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.

For more information about the California Prenatal Screening Program go to their website: Prenatal Screening Program

Last reviewed: January 12, 2017
Reviewed by: Kimberly Barr, MS, LCGC