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Maternal serum alpha-fetoprotein (MSAFP) testing is a prenatal screening blood test performed during pregnancy to help assess the risk of certain birth defects in the developing baby. Alpha-fetoprotein is a protein produced by the fetus, and small amounts normally pass into the mother's bloodstream. By measuring the level of this protein in maternal blood, healthcare providers can identify pregnancies that may be at increased risk for neural tube defects, abdominal wall defects, or chromosomal abnormalities.

The MSAFP test is typically performed between the 15th and 20th weeks of pregnancy, with the most accurate results obtained between weeks 16 and 18. The test measures the concentration of AFP in the mother's blood and compares it to expected normal values for that specific gestational age. Elevated MSAFP levels may indicate neural tube defects such as spina bifida or anencephaly, or abdominal wall defects like gastroschisis. Lower than normal levels may suggest an increased risk for chromosomal disorders such as Down syndrome or Edwards syndrome.

It is important to understand that MSAFP is a screening test, not a diagnostic test. Abnormal results do not confirm the presence of a birth defect but rather indicate the need for further evaluation. Many factors can affect MSAFP levels, including incorrect dating of the pregnancy, multiple pregnancies, maternal weight, and maternal diabetes. If MSAFP results are abnormal, additional testing may be recommended, such as a detailed ultrasound examination, amniocentesis, or other specialized prenatal diagnostic procedures.

MSAFP testing is often performed as part of a multiple marker screening panel, which may include measurements of other substances in maternal blood such as human chorionic gonadotropin and estriol. These combined tests, sometimes called triple or quadruple screens depending on the number of markers measured, can provide more comprehensive risk assessment for various fetal conditions. Women should discuss the benefits, limitations, and implications of MSAFP testing with their healthcare provider to make informed decisions about prenatal screening.