Ultrasound screening: Status of markers and efficacy of screening for structural abnormalities.

Aneuploidy is a major cause of perinatal morbidity and mortality and can have a significant impact on expecting parents and their families. With early screening and diagnosis it is important to be able to educate parents regarding the potential impact of the diagnosis. This knowledge allows parents the opportunity to consider management options early in the pregnancy, permitting more time to mentally and emotionally prepare both for the course of the pregnancy, and after the birth of the child should the pregnancy continue. Prenatal screening provides pregnant women a non-invasive risk assessment for the most common aneuploidies. Those who are considered "high-risk" then have the option for additional diagnostic (invasive) testing. Prior to the 1980s, prenatal screening consisted of risk assessment through maternal age; however, with the advent of maternal serum biochemical analysis and ultrasound, the field of prenatal screening developed significantly. As biochemical and sonographic advances continued into the 1990s, the emphasis shifted to risk assessment in the first trimester, with the combination of maternal serum analytes and sonographic evaluation of the nuchal translucency.(1) Within the last decade, the introduction of non-invasive screening (NIPT/S) has shown great impact on the expansion and evolving practice of prenatal screening. Although in many places the standard for prenatal testing continues to include maternal serum analytes and sonographic evaluation, the role of each marker alone and in combination remains important. In the era of increasingly available screening tests, especially with NIPT/(NIPS), this article attempts to review the current role of ultrasound in prenatal care and elucidate the role of ultrasound markers in prenatal screening.