[First trimester prenatal diagnosis of structural fetal anomalies with three dimensional ultrasound--possibilities and limitations].

AIM: To assess the possibilities of first trimester three-dimensional (3D) ultrasound fetal morphology survey and to analyze its advantages and limitations.

METHODS: A retrospective study of 483 singleton pregnancies scanned between 11-14 weeks of gestation (w.g.) was performed in the University Hospital of Obstetrics and Gynecology "Maichin dom" and MC "Markovs", Sofia between Jan 2009 and Oct 2010. All cases were examined with conventional 2D ultrasound for assessment of fetal number, viability and biometry. In addition, ultrasound screening for chromosomal fetal anomalies by nuchal translucency measurement and nasal bone assessment was also performed. In all cases of structural fetal abnormality several 3D/4D volumes of the region of interest were acquired. The clinical relevance of each volume data set was analyzed.

RESULTS: Twenty-two cases of structural fetal abnormalities were detected throughout the study period. There were 4 cases of central nervous system anomalies (2--anencephaly, 1--holoprosencephaly, 1--open spina bifida); 6 cases of gastro-intestinal tract anomalies (3--omphalocele, 1--gastroschisis, 1--abdominal cyst, 1--diaphragmatic hernia); 1 case with megacystis, 2 cases with skeletal anomalies (1--club foot, 1--club hand); 2 cases with atrioventricular septal defect; 5 cases with increased NT > 3 MM (1--monosomy 45,XO, 2--rare genetic syndromes, 2--normal perinatal outcome); 2 cases with polymalformation syndromes (1--body stalk anomaly, 1--pentalogy of Cantrell). In most of the cases 3D ultrasound has contributed with additional information in relation to the type and severity of the structural defect. However, in all cases it was not the primary diagnostic tool needed for the establishment of the correct prenatal diagnosis.

CONCLUSION: Three-dimensional (3D) ultrasound is a new imaging modality which provides better visualization of the fetal anatomy and has the potential to improve the detection rate of structural fetal abnormalities in early gestation. However, 3D ultrasound in the first trimester only complements, rather than substitutes the conventional gray-scale imaging in B-mode.