RESUMEN
OBJECTIVE: To evaluate the detection rate of major fetal anomalies by mid-trimester routine ultrasound screening in a single center with low-risk population. MATERIAL AND METHOD: The present study was a cross sectional study. All pregnant women attending the antenatal clinic between January 1996 and December 2002 had routine ultrasound screening between 18-22 weeks'gestation. The ultrasonographic results were compared with the pregnancy outcome in aspects of prediction of major fetal anomalies. RESULTS: Three hundred and sixteen fetuses out of 29,839 (1.06%) had major anomaly. One hundred and forty four fetuses (45.57%) were diagnosed as having major anomaly by routine ultrasound screening. One hundred and seventy two fetuses (54.43%) were undiagnosed. The sensitivity, specificity, positive predictive value, and negative predictive value were 45.57%, 99.97%, 94.74% and 99.42% respectively. CONCLUSION: Although the rate of the detection of major congenital fetal anomaly was low, almost all lethal and life threatening anomalies could be diagnosed antenatally thus allowing the option of counseling, pregnancy termination, or selective referral.