Prenatal detection of major congenital malformations in a cohort of 19 367 Danish fetuses with a complete follow-up six months after birth

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.