Prenatal Screening and Diagnosis: Time for a Paradigm Shift

Abstract

Recent advances in genetics and imaging have ushered in substantial breakthroughs in screening and diagnosis for chromosomal and structural abnormalities. Thus, it is imperative that healthcare providers caring for pregnant individuals should re-examine established practices in prenatal screening and diagnosis. In the past, screening for chromosomal abnormalities was based almost entirely on Down syndrome. Pregnant individuals aged > 35 were considered at “high risk” or of “advanced maternal age” based on age alone; however, the advent of tests with high sensitivity for prenatal detection of chromosomal abnormalities should lead to abandoning that concept, at least from the perspective of chromosomal abnormalities. Given that first-trimester and second-trimester screening will fail to detect between 5 and 20% of Down syndrome, in most situations, non-invasive testing with cell-free DNA should be the first-line screen for Down syndrome. The fact that over 99% of fetuses with Down syndrome will be detected prenatally with cell-free DNA gives other fetal chromosomal and structural abnormalities increasing prominence. Chromosomal microarray analysis (CMA) permits prenatal detection of several clinically important chromosomal aberrations that cannot be detected by karyotype and may exist in structurally normal fetuses with low-risk cell-free DNA screening. As such, CMA should be more readily conducted when invasive testing is performed, regardless of the presence of a structural abnormality. Isolated sonographic “soft markers” have no clinical significance in patients who have normal cell-free DNA screening, can cause unwarranted anxiety and a negative impact on pregnancy, and perhaps it is time to stop discussing them. Detailed first-trimester ultrasound allows early detection of several severe fetal anomalies, and therefore in settings with adequately trained personnel and resources, should be used more frequently. This Opinion traces the evolution of prenatal screening and diagnosis and advocates for a paradigm shift that aligns with recent developments in prenatal screening and diagnostic capabilities.