RESUMEN
The purpose of this paper is to discuss the minimal requirements of the routine mid-trimester anomaly scan in Asian countries after taking into account various factors, including local circumstances, medical practice, guidelines, and availability of experienced sonographers and high-resolution ultrasound machines, which affect the prenatal detection rate of fetal anomalies. In general, a routine mid-trimester anomaly scan includes the assessment of the number of fetuses, fetal cardiac activity, size, anatomy, liquor and placental location. The most controversial issue is which fetal structures should at least be examined. We discussed the requirements of a basic routine scan, as well as the optional views, which can be obtained if feasible to improve the detection of fetal, placental or maternal abnormalities. Routine anomaly scan remains a clinical challenge.