Performance of a first-trimester early anatomy ultrasound clinic in a high-risk population: a two-year implementation...

The standard fetal anatomic survey is performed by ultrasonography between 18 and 22 weeks of gestational age. Advances in ultrasonography technology have driven a move toward early anatomy surveys performed between 11 and 14 weeks. At this gestation, detection rates for fetal anomalies range from 20% to 80%. Earlier detection offers opportunities for genetic screening, informed counselling, and earlier decision-making regarding possible pregnancy interventions.

We evaluated the performance of a newly established first-trimester early anatomy ultrasound clinic at a tertiary care center serving high-risk patients, characterizing completion rates and diagnostic accuracy during its first 2 years of operation.

Retrospective cohort study of all pregnant individuals who underwent a first-trimester anatomy scan between 11+0 and 14+6 weeks of gestation at a tertiary center between September 2020 and December 2022. Primary outcomes were completion rate and diagnostic accuracy compared with routine second-trimester anatomy scan results.

A total of 184 first-trimester anatomy scans were performed. Complete anatomical survey was achieved in 90 scans (48.9%). The most commonly nonvisualized structures were the nose and lips (22.8%), cardiac structures (15.8%), and spine (14.1%). Including a case of termination of pregnancy based on early anatomy findings, the prevalence of fetal anomalies was 4.9%. Sensitivity for anomaly detection was 62.5% (95% CI: 30.6%-86.3%); specificity was 98.0% (95% CI: 94.2%-99.3%); positive predictive value was 62.5% (95% CI: 30.6%-86.3%); negative predictive value was 98.0% (95% CI: 94.2%-99.3%). The false positive rate was 2.0%. Among cases with missed anomalies, none were attributable to nonvisualized structures on early anatomy.

Approximately half of high-risk patients achieved a complete first-trimester anatomical survey at our clinic. Detection sensitivity was 62.5% with a low false positive rate, and missed anomalies on routine anatomy were not related to incomplete visualization on early anatomy. These findings support early anatomy ultrasound as a complementary tool to routine mid-trimester anatomical survey in high-risk populations. El resumen está disponible en Español al final del artículo.