What is Maternal Serum Screening?
Maternal serum screening is a blood test conducted during pregnancy to assess the risk of certain genetic conditions in the fetus. This non-invasive test measures the levels of specific substances in a pregnant woman's blood to determine the likelihood of chromosomal abnormalities, such as Down syndrome, trisomy 18, and neural tube defects like spina bifida.
When is Maternal Serum Screening Performed?
Maternal serum screening is typically performed in the first and second trimesters of pregnancy. The
first-trimester screening usually occurs between 11 and 14 weeks of gestation and includes measurements of pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin (hCG). The
second-trimester screening, also known as the quadruple test, is done between 15 and 20 weeks and measures alpha-fetoprotein (AFP), hCG, estriol, and inhibin-A.
How Does Maternal Serum Screening Work?
The test involves drawing a blood sample from the pregnant woman. The levels of the substances measured are compared to typical values for the same stage of pregnancy. The results are then combined with other factors, such as maternal age and gestational age, to calculate the risk of specific conditions. The screening provides a risk estimate, not a definitive diagnosis.
What Do the Results Mean?
The results of maternal serum screening are given as a risk ratio, such as 1 in 250 or 1 in 1,000. A high-risk result does not mean the fetus definitely has a condition, but it indicates a higher likelihood, prompting further diagnostic testing. Conversely, a low-risk result means the likelihood of a condition is lower, but it does not guarantee the absence of a condition.
Are There Any Risks Associated with Maternal Serum Screening?
Maternal serum screening is a safe and non-invasive procedure with no direct risks to the mother or fetus. However, it can cause anxiety due to the uncertainty of the results and the potential for false positives or false negatives. It is important to discuss the benefits and limitations of the screening with a healthcare provider.
Advanced maternal age
Family history of genetic disorders
Previous pregnancy with a chromosomal abnormality
Exposure to harmful substances during pregnancy
Conclusion
Maternal serum screening is a valuable tool in prenatal care, providing critical information about the risk of genetic conditions in the fetus. While it is not diagnostic, it helps guide further testing and decision-making. Consulting with a healthcare provider and genetic counselor is essential to understand the implications of the results and the best course of action.
