The value of detailed first-trimester ultrasound in the era of non-invasive prenatal testing.

BACKGROUND: In 2020, the American College of Obstetricians and Gynecologists recommended non-invasive prenatal testing be offered to all patients. However, current society guidelines in the United States do not universally recommend a detailed first-trimester ultrasound.

OBJECTIVE: This study aimed to determine the additional findings identified through first-trimester ultrasound that would have otherwise been missed if non-invasive prenatal testing was used alone as a first trimester screening method.

STUDY DESIGN: This was a retrospective cohort study involving 2,158 pregnant patients, 2,216 fetuses that were seen at a single medical center between January 1, 2020 and December 31, 2022. All those included underwent both non-invasive prenatal testing and detailed first-trimester ultrasound between 11.0 - 13.6 weeks gestation. Non-invasive prenatal testing results were categorized as low-risk or high-risk and first-trimester ultrasound results were categorized as normal or abnormal. Abnormal first-trimester ultrasounds were further classified as first 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). Descriptive statistics were used to report our findings.

RESULTS: Sixty-five (65/2216, 3%) fetuses had a high-risk non-invasive prenatal testing result, while 2,151 (2151/2216, 97%) fetuses had a low-risk non-invasive prenatal testing result. Of those with a low-risk non-invasive prenatal testing result, 2,035 (2035/2151, 94.6%) had a normal first-trimester ultrasound while 116 (116/2151, 5.4%) had at least 1 abnormal finding on first-trimester ultrasound. The most common screening marker detected within the low-risk non-invasive prenatal testing group was absent nasal bone (52/2151, 2.4%), followed by reversed a-wave of the ductus venosus (30/2151, 1.4%). The most common structural defect in this group was cardiac in nature (15/2151, 0.7%). Overall, 181 fetuses were identified as having "abnormal screening" through either a high-risk non-invasive prenatal testing result (n = 65) or through a low-risk non-invasive prenatal testing result but abnormal first-trimester ultrasound (n = 116). In summary, the incorporation of first-trimester ultrasound screening identified 116 additional fetuses (116/2151, 5.4%) that required further follow-up and surveillance than non-invasive prenatal testing alone would have identified.

CONCLUSION: Detailed first-trimester ultrasound identified more fetuses with a potential abnormality than non-invasive prenatal testing alone. Therefore, first-trimester ultrasound remains a valuable screening method that should be used in combination with non-invasive prenatal testing.