(1119) Routine use of the Detailed First Trimester Ultrasound (DFTU) and Associated Outcomes

As many states incorporate gestational age limits on elective termination, the identification of congenital anomalies (3-5% in the general population) in the first trimester becomes paramount to having the ability to choose elective termination.  We sought to determine the anomaly rate, types of anomalies, and outcomes detected on the DFTU.

Study Design:

At our large, academic teaching hospital, we offer all pregnant patients a DFTU regardless of risk.  We performed a retrospective cohort study of our database between February 23, 2022 and March 31, 2023. All examinations were performed by the division of Maternal Fetal Medicine.


Results:

A total of 3748 pregnant patients received a DFTU exam, of which 3715 (99.1%) were available for analysis. 41 (1.10%) had at least one fetal anomaly noted. There were demographic differences between the two cohorts. Anomaly detection rate on second trimester anatomy ultrasound was significantly higher in the anomaly on DFTU group (41.7% versus 1.3%, p < 0.001). Additionally, anomaly on DFTU was associated with a significantly higher risk of high risk NIPT testing (47.2% versus 1.30%, p< 0.001), as well as higher rates of invasive testing using chorionic villous sampling (CVS) (9.75% versus 0.16%, p< 0.001) and amniocentesis (14.6% versus 0.49%, p< 0.001). The most common anomaly identified on DFTU was cystic hygroma, which was seen 58.5% of DFTUs with an abnormality. Less than half of DFTU abnormalities were revisualized on a detailed second trimester ultrasound, however 20% of DFTU revealed a different anomaly than was previously seen on the DFTU.  Of patients with an anomaly, 36/41 (87.8%) elected to have cell free DNA (cfDNA) screening, and of those who did have cfDNA screening 19/36 (52.8%) were negative.

Conclusion:

The rate of detecting an anomaly on the DFTU exam in our cohort was approximately 1 in 90 (1.1%).  Of those, over half had negative cfDNA screening.