Which tests are typically part of second trimester screening?

Second trimester screening typically includes the measurement of specific biomarkers in maternal serum that can help assess the risk of certain chromosomal abnormalities and other conditions in the developing fetus. One of the key components of this screening is the assessment of unconjugated estriol and maternal serum alpha-fetoprotein (AFP).

Unconjugated estriol is an estrogen produced by both the placenta and the fetus, and its levels can provide information about fetal well-being. Maternal serum AFP is a protein produced by the fetal liver, and its levels in the mother's blood can indicate the risk for conditions such as Down syndrome and neural tube defects. The combination of these markers allows for a better estimation of risk and helps guide further diagnostic testing if indicated.

In contrast, while a complete blood count (CBC) is important in monitoring maternal health, it does not provide information specific to fetal anomalies. Beta HCG is primarily utilized in the first trimester for pregnancy confirmation and can indicate certain conditions, but it is not part of the routine second trimester screening process. Chorionic villus sampling (CVS) is an invasive diagnostic procedure that is usually performed in the first trimester to obtain a sample of placental tissue for genetic testing, rather than a screening tool in the second trimester