Objective: Impact of Doppler system in detection of congenital malformations during prenatal diagnosis. Design: Prospective clinical study. Setting: Department of Medical Genetics and Foetal Medicine, Department of Obstetrics and Gynaecology University Hospital Olomouc. Methods: In 34 pregnancies with prenataly diagnosed congenital malformation the umbilical arte- ry pulsatility index (PI) and middle cerebral artery PI were assessed. Results: Abnormal Doppler patterns were obtained in 18 patients (chromosomal abnormalities - 3x, gastroschisis - 2x, diaphragmatic hernia - 2x, urinary tract abnormalities - 2x, internal hydro- cephalus - 4x, microcephaly, anencephaly, encephalocoele, non-immune hydrops of the fetus, thoracopagus - 1x). Conclusion: In accordance to the literature abnormal Doppler patterns in umbilical artery were obtained in trisomy 21 foetuses. The use of umbilical artery PI or ductus venosus PI in the first trimester of pregnancy as an additional parameter for screening purposes needs to be confirmed by further investigation (needs to be further explored). Pulsed Doppler waveform analysis gives a possibility to appreciate the functional state of the foetus. In our patient group abnormal Doppler patterns were found in such substantial congenital malformations that they indicated pregnancy termination themselves. On the other hand in seve- ral similar morphological defects normal Doppler patterns were found. In these cases, in regard to the type of malformation,

        Key words: Doppler ultrasonography, prenatal diagnosis, congenital malformation