Summary of California Prenatal Screening Tests
During your pregnancy, your prenatal care provider should offer you two prenatal screenings as part of the California Prenatal Screening Program. Each screening requires you to give a blood sample. Each screening estimates the chances of your fetus having one of the genetic conditions or birth defects screened for in the Prenatal Screening Program.
Below are the details about the two types of prenatal screening offered by the state program. See also program resources at the bottom of the page.
Cell-free DNA (cfDNA)Screening
What it screens for: Genetic conditions
Cell-free DNA (cfDNA) screening of your blood sample uses genetic information from the placenta to check the fetus for the chances of it having the genetic conditions below. The placenta is the organ inside a pregnant individual that provides nutrients and oxygen to the fetus.
- Trisomy 21 (Down syndrome)
- Trisomy 18 (Edwards syndrome)
- Trisomy 13 (Patau syndrome)
When to get it: cfDNA screening is recommended from 10 weeks to the first day of 21 weeks of pregnancy. The screening can be done after the first day of 21 weeks of pregnancy but the follow-up services are then more limited. Screening results are available in 10 to 14 days.
Maternal serum alpha-fetoprotein (MSAFP) screening
What it screens for: Neural tube defects
Maternal serum alpha-fetoprotein (MSAFP) screening of your blood sample looks at the protein made by the developing fetus. The amount of the protein may show whether the fetus has a birth defect called a neural tube defect. The most common types of these defects are:
- Open spina bifida (opening in the spine)
- Anencephaly (missing parts of brain or skull)
When to get it: MSAFP can be done from 15 weeks to the first day of 21 weeks of pregnancy. Screening results are available in 7 to 10 days.
After Prenatal Screening
Most pregnancies result in a healthy baby. But 3 or 4 out of 100 fetuses may have a genetic condition or birth defect.
If prenatal screening finds no increased chance of your fetus having one of the genetic conditions or birth defects screened for, no further services will be offered by your prenatal care provider from the state program.
If prenatal screening finds an increased chance of your fetus having one of the genetic conditions or birth defects screened for, your prenatal care provider should offer you the option of getting genetic counseling, an ultrasound exam, and diagnostic testing to learn more about whether your fetus has the birth defect. Diagnostic testing includes chorionic villus sampling (CVS) and amniocentesis.
When you get prenatal screening through the state program, the follow-up services are provided at a state-approved Prenatal Diagnosis Center at no additional cost. You decide if you want any of the follow-up services.
Genetic counseling is the first service provided at a stateapproved Prenatal Diagnosis Center. A genetic counselor
discusses your screening result and what it means. You
will also review your family’s health history. The genetic
counselor will give you information about the other
follow-up services available to you.
The counselor will explain that you have several options
that include ultrasound and chorionic villus sampling or
amniocentesis. Be sure to ask the genetic counselor any
questions you may have.
You decide if you want any services after genetic counseling.
Doctors with special training can do a high-level ultrasound, in
general starting from 12 weeks of pregnancy. It gives a very
detailed picture of the fetus.
An ultrasound checks the age of the fetus. It may identify some
birth defects. However, it is not a way to find out for certain if
your fetus does have a genetic condition.
You can have this ultrasound even if you decide not to have
chorionic villus sampling or amniocentesis.
Chorionic villus sampling
Chorionic villus sampling (CVS) is a test that can tell if the fetus
has a genetic condition. CVS can be done from 10 through the
end of 14 weeks of pregnancy.
For this test, an experienced doctor removes a small amount
of tissue using a very thin needle or tube. The fetus is not
touched. The tissue contains the same chromosomes as the
fetus. The chromosomes are counted and examined.
CVS is considered a safe test when performed by a medical
expert at a state-approved Prenatal Diagnosis Center.
The risk of miscarriage due to CVS is small – less than
1 in 450. The CVS result is usually ready in two weeks.
Amniocentesis is a test that can tell if the fetus has a genetic condition. This test can be done starting from 15 weeks of
For this test, an experienced doctor takes a small amount
of the fluid around the fetus with a thin needle. The fetus
is not touched. This fluid contains cells from the fetus. The
chromosomes in these cells are counted and examined.
Amniocentesis is considered a safe test when done by a
medical expert at a state-approved Prenatal Diagnosis Center.
The risk of miscarriage due to amniocentesis is small – less
than 1 in 900. The amniocentesis result is usually ready in two
- Birth Defects Screened for by the PNS Program
- Education Resources for Individuals and Families
- Getting an Unexpected Screening Result
- Prenatal Screening Patient Video (English, MP4, 3.29 min) ... (Spanish, MP4, 4.14 min) ... (Chinese, MP4, 3.59 min)
- Prenatal Screening Patient Booklet - English (PDF, 12 pages, 1.3 MB) ... Spanish (PDF) ... Chinese, Simplified (PDF, 24.4 MB) ... Korean (PDF) ... Tagalog (PDF) ... Vietnamese (PDF) ... Russian (PDF) ... Armenian (PDF) ... Farsi (PDF) ... Hmong (PDF)
- Patient Booklet Summary - English (PDF, 2 pages) ... Spanish (PDF) ... Chinese, Simplified (PDF) ... Korean (PDF) ... Tagalog (PDF) ... Vietnamese (PDF)
Patient Booklet Summary
- These summaries should be used in addition to the patient booklets, not instead of them. It is important that each patient receive the patient booklet. The patient booklet includes a full description of the program and its components, what consent means, and mandated legal notices.