Sequential Integrated Screening
Sequential 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:
- Down syndrome
- Trisomy 18
- Neural Tube Defects (anencephaly and spina bifida)
- Abdominal Wall Defects (gastroschisis and omphalocele)
- Smith-Lemli-Opitz syndrome (SLOS)
Sequential Integrated Screening has three separate steps: two blood tests and one ultrasound.
First trimester blood test (10 to 13 weeks): Sequential 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.
Nuchal translucency ultrasound (11 to 14 weeks): The second step for Sequential Integrated Screening is a special ultrasound done from 11 weeks 2 days to 14 weeks 2 days of the pregnancy. This ultrasound measures an area on the fetal neck called the "nuchal translucency" (NT). The NT ultrasound lets the program calculate an initial (preliminary) result for Down syndrome and trisomy 18 and provides early screening for some physical birth defects.
Second trimester blood test (15 to 20 weeks): The final step of Sequential 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
SCREENING RESULTS
When are results available?
Sequential Integrated Screening will give you results at two separate times. The first (preliminary) result is available soon after you have both the first trimester blood test and the NT ultrasound. The second (final) result is available one to two weeks after the second blood test.
If your preliminary result is screen positive, a genetic counselor will talk with you about your result. You are offered the option of having a diagnostic test, either CVS or amniocentesis; or you can choose to complete Sequential Integrated Screening before making a decision about diagnostic testing. If you choose Sequential Integrated Screening, you will get your final result after the second trimester blood test.
What type of result is reported?
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
For more information about the California Prenatal Screening Program go to their website: Prenatal Screening Program
Last reviewed: December 7, 2017
Reviewed by: Kimberly Barr, MS, LCGC