CALIFORNIA PRENATAL SCREENING PROGRAM 1st and 2nd Trimester Screening:
A Prenatal Test for Chromosomal Conditions and Common Birth Defects
What is the California Prenatal Screening Program 1st and 2nd Trimester Screening?
This screening program is a non-invasive, step wise test that collects information about your pregnancy from the first trimester and the second trimester and integrates it in order to provide you with a personalized risk assessment for:
• Down Syndrome
• Trisomy 18 (severe mental retardation and birth defects)
• Open spine defects such as spina bifida
• Smith Lemli Opitz Syndrome (SLOS) (a rare form of mental retardation)
This screening test will allow you to become better informed about the risks of these conditions to your pregnancy. Please remember that this is only a risk assessment. This test is NOT intended to diagnose the pregnancy with any of these conditions. If the testing reveals an increased risk, then genetic counseling and diagnostic testing options are available.
How is this test performed?
There are two steps that are performed in this screening program, one in the first trimester and one in the second trimester of pregnancy. Step 1 consists of a first trimester blood draw and an ultrasound measurement of the neck region (nuchal translucency) of your fetus. These two parts of the screening test must be completed in the first trimester. The blood test can be performed between 10 weeks 0 days to 13 weeks 6 days of pregnancy. The blood can be collected at our office before your NT ultrasound appointment or it can be collected on the same day as your NT ultrasound. If you choose to come to our office and have your blood collected one week before your NT ultrasound, you will receive a preliminary result at the time of your ultrasound. The ultrasound examination is performed between 11 weeks 2 days to 14 weeks 2 days of pregnancy.
Step 2 consists of one second trimester blood draw which is performed in the second trimester of pregnancy, between 15 weeks 0 days to 20 weeks 0 days.
Do I receive any results after Step 1?
You will receive PRELIMINARY results after you complete the first trimester blood draw and the NT ultrasound. The preliminary results will provide you with a risk assessment for Down syndrome and Trisomy 18. If your blood was drawn at least one week in advance of your NT ultrasound, you will receive your preliminary results on the day of your NT ultrasound. If your blood was drawn on the day of your NT ultrasound, then you will receive your preliminary results approximately 1-2 weeks after your ultrasound.
What if my preliminary result indicates an increased risk (screen positive) for Down syndrome or other abnormalities?
Do not panic! In most cases your baby will not have Down syndrome. You will be offered genetic counseling to discuss your screening results and options for further screening or diagnostic testing. Diagnostic testing options may include chorionic villus sampling (CVS) performed at 10 to 12 weeks 6 days of pregnancy or amniocentesis performed at 16 to 20 weeks of pregnancy.
You may also choose to proceed to Step 2 of the state screening program and decide about diagnostic testing after your final screening results are available.
What if my preliminary result is screen negative?
A preliminary screen negative result is reassuring; however the test is NOT complete until you complete Step 2. Detection rates for Down syndrome and Trisomy 18 are higher when both Step 1 and Step 2 of the testing have been completed. In addition, Step 2 will provide you with a risk assessment for open spine defects and Smith Lemli Opitz syndrome (SLOS).
How will I receive my final results?
Your final results will be available approximately 1-2 weeks after you have completed Step 2. The results from Step 1, the first trimester blood draw and NT ultrasound, and Step 2, the second trimester blood draw, are integrated to provide you with a FINAL risk assessment for Down Syndrome, Trisomy 18, open spine defects, and Smith Lemli Opitz syndrome (SLOS). These final results are the best overall risk assessment for your pregnancy.
What if my final result indicates an increased risk (screen positive) for any of these conditions?
A final screen positive result does not mean that the baby has the condition; the majority of pregnancies at increased risk will NOT be affected. You will be offered genetic counseling to review your results and your options for further testing. This may include diagnostic testing such as amniocentesis. Comprehensive fetal ultrasound can also be used to gather more information about risks for Down syndrome, Trisomy 18, open spine defects and abdominal wall defects
What if my final result is screen negative?
You were not identified to be at increased risk for Down syndrome, Trisomy 18, open spine defects and Smith Lemli Opitz syndrome (SLOS).
Will this test identify all cases of Down syndrome, Trisomy 18, open spine defects and SLOS?
The California state screening program 1st and 2nd trimester screening test will detect approximately 90% of cases of Down syndrome, 81% of Trisomy 18, 80% of open spine defects, and 60% of SLOS. Diagnostic testing such as amniocentesis is always available.
Can this testing be performed on twins?
Yes, although detection rates are slightly lower.
If you have additional questions please feel free to contact our office at 415-202-1200 to schedule a genetic counseling appointment. We are available to answer your questions and help in any way that we can.