Routine ultrasound screening and detection of congenital anomalies outside a university setting.

BACKGROUND: To assess the sensitivity for detecting fetal congenital anomalies by a routine ultrasound examination program at midtrimester performed in an unselected population by midwives and specialists in obstetrics and gynecology.
METHODS: Six hundred seventy-six of the pregnancies had the midtrimester ultrasound examinations performed outside the county. Three hundred seventeen of the women had midtrimester ultrasound examinations performed in the county, but delivered outside the county. A total of 18 181 pregnancies were eligible for the study.
RESULTS: Altogether there were 267 fetuses and newborns with anomalies, which gives a prevalence of 1.5%. One hundred three of the 267 anomalies were detected at the midtrimester ultrasound examination, yielding a sensitivity of 39.0%. There were 11 false positives and 163 remained undiagnosed (false negatives), which gives a specificity of 99.9% and a positive predictive value of 90.4%. The sensitivity for detecting anomalies ranged from 74.4 to 8.3% according to the organ system of the fetus.
CONCLUSIONS: Our study shows that midtrimester routine ultrasound examination in district hospitals can achieve a detection rate of congenital anomalies comparable with tertiary centers. One-stage ultrasound examination at midtrimester gives acceptable results concerning congenital anomalies with few false-positive results.