Genetics Northern California


Maternal Serum Alpha Fetoprotein (MSAFP) Screening is an optional blood test done between 15 to 21weeks in pregnancy. This test is part of the California Prenatal Screening Program and is offered to all pregnant people in California. The test looks for certain birth defects during pregnancy.  The choice to have this test is up to you.  

Below is a list of the conditions the test can help detect:

Blood Test 2

This test measures a protein called alpha-fetoprotein (AFP), which is found in the blood during pregnancy.  AFP is made by the baby's liver. It passes through the placenta into a pregnant person's blood.  

The amount of AFP 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 blood test


Results are usually available one to two weeks after the blood test.  You can find the results posted on

What type of results could I get? 
  • Screen negative (low risk) - This means that the chance is low for the baby to have any of the conditions the test looks for. Most people will get screen negative results. 
  • Screen positive (high risk) - This means that the chance for the baby to have a birth defect is high enough to offer follow-up testing. More testing is needed to know for sure.

Kaiser members with screen positive results are offered genetic counseling and follow-up services at a local Kaiser Permanente Genetics Department. Follow-up can also happen at any of the State-approved Prenatal Diagnosis Centers.  There is no additional fee for authorized follow-up services. 

Click here for more information about the California Prenatal Screening Program.  

Last reviewed: September 21, 2022
Reviewed by: Kimberly Barr, MS, LCGC