Prenatal Screening Technologies and Test Issues
Maternal serum screening began with the measurement of serum alpha fetal protein to detect open neural tube defects, which led to the implementation of routine serum-based prenatal screening in the second trimester for Down syndrome. Advances via combined and integrated screening allowed for the first-trimester detection of both Down syndrome and trisomy 18. Next-generation sequencing has enabled the identification of aneuploidies in circulating cell-free fetal DNA from the plasma fraction of maternal whole blood. This breakthrough in molecular genetic testing, commonly referred to as noninvasive prenatal testing, has revolutionized prenatal screening and testing for genetic disorders without posing additional risk to the pregnancy. This chapter reviews the history of maternal serum screening, the disorders it can detect, the methods of calculating patient-specific risk, and reasons for recalculation or adjustment of risk. This chapter also reviews of cell-free DNA-based testing for fetal aneuploidies, including its limitations and potential.