Lene Sperling

Introduction To investigate the performance of the second‐trimester ultrasound scan regarding ultrasound‐detectable congenital malformations in a Danish region. The study sample was population‐based, with 6 months of postnatal follow‐up. Hospital records and autopsy reports were reviewed in each case to validate the prenatal ultrasound diagnosis. Material and methods This population‐based cohort study included all fetuses ( n = 19.367) alive at the second‐trimester scan in four hospitals in a Danish region. The final diagnosis of the malformations was based on hospital records during the 6‐month postnatal follow‐up. In case of termination or stillbirth, the result from the autopsy report was used to validate the prenatal ultrasound diagnosis. Results The detection rate of congenital malformations in the prenatal screening program was 69%, where 18% was detected on the first‐trimester scan and 51% on the second‐trimester scan. Another 8% was detected in the third trimester. Specificity was 99.9%. The positive predictive value of the screening program was 94.5%, and the negative predictive value was 99.5%. The overall prevalence of malformations was 16.8 per 1000 fetuses, most frequently in the heart and the urinary tract. Conclusions This study shows that the national screening program for congenital malformations can detect many severe malformations and is an effective screening test for malformations.