What is indicated by a maternal serum screen result showing decreased alpha-fetoprotein (AFP)?

A decreased level of alpha-fetoprotein (AFP) in a maternal serum screen is particularly indicative of an increased risk for Down syndrome, also known as trisomy 21. AFP is a protein produced by the fetal liver that is present in the mother's blood during pregnancy.

When the AFP level is lower than the expected range, it can signal chromosomal abnormalities, most notably Down syndrome. This is because, in cases of Down syndrome, the production of certain proteins, including AFP, is often altered, leading to lower levels detectable in maternal blood.

Additionally, a reduced AFP level may also be associated with other types of chromosomal issues or conditions, but the most significant association in screening tests is with Down syndrome. Therefore, women with decreased AFP levels are typically recommended for further testing, such as ultrasound or amniocentesis, to assess for potential chromosomal abnormalities.

Understanding the significance of the AFP levels is crucial in prenatal screening as it helps in early identification and management options for the mother and her baby.