Challenges in Sonographic Detection of Fetal Major Structural Abnormalities at the First Trimester Anomaly Scan

First-trimester (FT) ultrasound examination appears to have a very good sensitivity in the detection of fetal abnormalities, especially when an extended protocol that is achievable with reasonable resources of time, personnel and ultrasound equipment, is used. It has been shown that the efficiency of the routine anomaly scan varies widely between the studies performed both in early or mid-pregnancy. The analysis of technique and study designs reveals that in each gestational age, the extension of the investigational protocol is the most important factor in modulating the detection rate. Moreover, the use of similar basic checklists at the FT and second trimester (ST) examinations revealed comparable anomaly detection rates in large population groups. First trimester combined test have been demonstrated as a useful screening tool for genetic syndromes and consecutively the FT ultrasound scan became a routine examination in most prenatal diagnostic centers. Its performance in structural abnormalities detection has been communicated in high-, medium-risk populations or unselected low-risk variable number of patients and compared to the ST anomaly scan effectiveness. A detailed first-trimester anomaly scan using an extended protocol is an efficient screening method to detect major fetal structural abnormalities in lowrisk pregnancies. It is a method that it is feasible at 12 to 13 + 6 weeks with ultrasound equipment and personnel already used for routine first-trimester screening. Rate of detection of severe malformations is greater in earlythan in mid-pregnancy and on postnatal evaluation. Early heart investigation could be improved by an extended protocol involving use of color Doppler.