Soft markers for aneuploidy following reassuring first trimester screening: what should be done?

The present article aims to review the current role of the soft markers on the second trimester ultrasound (STUS) in women after reassuring first trimester screening (FTS) in singleton pregnancies.

Improvements in the FTS and the recent implementation of noninvasive prenatal testing (NIPT) for common aneuploidies have important impact on the prevalence of these conditions in the STUS. Some studies suggest that soft markers in the second trimester of the fetus without structural anomalies have a minor or no role in Down syndrome detection in a prescreened population with reassuring results. However, NIPT could be offered as a next step in the management of such pregnancies if the calculated new composite risk (NCR) for aneuploidy is increased. In the case of reassuring results, pregnancy follow-up for certain markers is advised.

NIPT has emerged as a new method of prenatal testing and is feasible in the second trimester in women with increased NCR. However, apart from the Down syndrome screening, STUS screening remains a powerful tool in screening for other fetal aneuploidies, structural anomalies and pathological placental conditions and detection of specific soft markers that require pregnancy follow-up.