(800) The value of detailed first trimester ultrasound in the era of non-invasive prenatal testing

In 2020, the American College of Obstetricians and Gynecologists (ACOG) recommended non-invasive prenatal testing (NIPT) be offered to all patients for routine first trimester screening. However, there is no such guideline for detailed first trimester ultrasound (FTU), despite previous studies documenting its important screening capabilities. Our aim was to describe the added benefit of FTU in the era of universal NIPT.

Study Design:

This was a large retrospective study involving pregnancies from a single medical center that underwent both NIPT and detailed FTU between January 2020-January 2022. NIPT results were categorized as low risk or high risk and FTU results were categorized as normal or abnormal. Abnormal FTUs were further classified as 1^st trimester screening markers (increased nuchal translucency, absent nasal bone, tricuspid regurgitation, ductus venosus reverse a-wave) or structural defects (cranium, neck, heart, thorax, abdominal wall, stomach, kidneys, bladder, spine, extremities) and grouped according to finding.

Results:

A total of 1096 pregnancies were included, 1070 singleton and 26 twins, for a total of 1122 fetuses. 45 fetuses (4%) had a high risk NIPT, while 1077 fetuses (96%) were low risk. 1032 fetuses (92%) had a normal FTU, while 90 fetuses (8%) had at least 1 abnormal finding. (Figure 1) Of the 146 abnormalities detected, 98 were 1^st trimester screening markers, involving 59 (5.3%) fetuses, and 48 were structural defects, involving 31 (2.8%) fetuses. The most common screening marker detected was absent nasal bone (41/146, 28%). The most common structural defect was cardiac in nature (17/146, 11.6%). Overall, 116 fetuses were screened high risk either by NIPT (n = 26), FTU (n = 71), or by both NIPT and FTU (n = 19). In summary, the incorporation of FTU screening identified 71 additional fetuses (6.3%) that would have otherwise been screened low risk by NIPT alone. (Figure 2)

Conclusion:

FTU identified more fetuses with a potentially high-risk abnormality than NIPT alone. Therefore, FTU remains a valuable screening method that should be used in combination with NIPT.