P05.14: Routine screening for fetal anomalies in the 12th week of pregnancy (1996–2012): advantages and limitations

Abstract

Evaluation of the advantages and limitations of routine screening in early pregnancy by transvaginal sonography in an unselected population. Routine ultrasound examination was offered to every woman in the 12th week of her pregnancy using a transvaginal probe. The examination protocol was focused on surching for major structural anomalies. Routine transabdominal screening at 18 and 32 weeks was also performed. Anomalies were divided into three groups. Group 1: all cases were diagnosed; Group 2: only a certain percent of the cases were detected; Group 3: not detected. Diagnoses were confirmed by neonatological and pathological examinations In a seventeen-year period 22195 women were examined and 393 fetuses had malformations. Fetal anomalies were diagnosed in 130 cases at the 12th week (33,3%), 94 cases at 18 weeks (23,9%), 138 cases at 32 weeks (35,2%) and 29 cases later. All those malformations which cause severe defects and/or extensions of the body contour were detected (Group 1). Structural anomalies which can be diagnosed as a consequence of obstruction or stenosis and those causing small defects were recognised only in a certain percent of cases (Group 2). The explanation for the failure to detect the anomalies included in Groups 2 and 3 is discussed. Early transvaginal screening offers the possibility of early termination of pregnancies with severe structural anomalies in 33,3% of cases. However standard mid-second-trimester transabdominal scanning is still recommended since a significant number of malformations cannot be detected so early in pregnancy. (a) There are malformations which do not manifest so early in pregnancy; (b) we do not have enough experience of the early pathological changes of these anomalies; (c) the resolution of the transvaginal probe is still not enough to recognise them.