OBJECTIVE: This study assessed the percentage and type of congenital anomalies diagnosed at first-trimester ultrasound (US) scan in a primary care setting without following a standardized protocol for fetal anatomical assessment.
MATERIALS AND METHODS: US scans performed between 11+0 and 13+6 weeks of gestation in pregnancies with estimated date of delivery between January 1, 2012 and January 1, 2016 were searched. Data were supplemented with results of 20-week scans and pregnancy outcome.
RESULTS: Of all scans, 38.6% were dating scans and 61.4% were part of first-trimester screening. Anomalies were diagnosed prenatally in 200 (1.8%) fetuses; 81 (0.7%) were chromosomal and 119 (1.1%) were structural. Of all prenatally detected anomalies, 27% (n = 32) were detected at first-trimester scan, with a false-positive rate of 0.04%. All cases of anencephaly (n = 4), encephalocele (n = 2), exomphalos (n = 9), megacystis (n = 4), and limb reduction (n = 1) were diagnosed. First-trimester detection of gastroschisis and congenital heart defects was 67 and 19%, respectively.
CONCLUSION: In a primary care setting, global fetal anatomical assessment at first-trimester scan without following a standardized protocol detects about 30% of all structural anomalies and most of the severe anomalies, with an extremely low false-positive rate. We hypothesize that additional training and use of a systematic protocol would improve early detection of structural anomalies.