The detection rate of congenital morphological abnormalities during ultrasound examinations in early pregnancy is not sufficient with B-mode alone due to the small size of the target. This study aimed to evaluate the effectiveness of routine color Doppler mode compared to B-mode alone in the early detection of congenital heart disease (CHD) during first-trimester screening.

A before-after clinical study was conducted at Showa University Hospital between January 2012 and May 2023. In April 2018, the protocol was modified to incorporate routine color Doppler mode. We compared detection rates, specificity, positive predictive values (PPV), and negative predictive values (NPV) between the B-mode only group and the B-mode with routine color Doppler group.

Among the 12,321 fetuses screened, 5,907 were screened with B-mode only and 6,414 with routine color Doppler mode. The detection rate for CHD was significantly higher with color Doppler mode (29.26% vs. 64.15% for all CHDs, p < 0.001; 48% vs. 85.71% for major CHDs, p = 0.001) without impairing the specificity (99.96% vs. 99.98%) or PPV (94.44% vs. 92.31%).

Routine use of color Doppler mode in first-trimester CHD screening significantly increases detection rates while maintaining high specificity and PPV. This protocol supports early CHD diagnosis, facilitating timely prenatal counseling and management.