To evaluate whether the quality scores validated for second-trimester ultrasound scan can be used for third-trimester ultrasound scan.

Prospective multicenter ancillary study using data from the RECRET study. Nulliparous women, with no reported history, with second- and third-trimester ultrasound examinations performed by the same ultrasonographer and using the same ultrasound machine were recruited. The global score and the individual score of each ultrasound image were compared between second- and third-trimester ultrasound scan. The sample size was calculated for a non-inferiority (one-sided) paired Student t test.

103 women with 1606 anonymized ultrasound images were included. The median term at second- and third-trimester ultrasound scan was 22.2 weeks gestation (22.0–22.7) and 31.6 weeks gestation (30.7–34.7), respectively. The mean global score of ultrasound images was comparable between the second- and the third-trimester ultrasound examination (32.37 ± 2.62 versus 31.80 ± 3.27, p = 0.13). Means scores for each biometric parameters i.e. head circumference, abdominal circumference, and femur diaphysis length were comparable. The scores for the four-chamber view (5.11 ± 0.91 versus 5.36 ± 0.75, p = 0.02) and the spine (4.18 ± 1.17 versus 5.22 ± 1.02, p < 0.001) were significantly lower in the third trimester compared to the second trimester. The score for the kidney image was significantly higher for third trimester images compared to second trimester images (4.73 ± 0.51 versus 4.32 ± 0.67, p < 0.001.

Biometrics parameters quality scores images previously validated for the second trimester ultrasound scan can be also used for the third trimester scan. However, anatomical quality scores images performances may vary between the second and the third trimester scan.