RECENT ADVANCES IN THE DOPPLER STUDY OF EARLY FETOMATERNAL CIRCULATION

Transvaginal color DopPler has enabled precise investigation of feto-m aternal circulation in early pregnancy. Decrease of peripheral impedan ce, as well as increase of blood flow velocity was found in all segmen ts of the uteroplacental circulation with gestational age. The same fi nding was observed in umbilical artery, fetal aorta and intracranial b lood vessels. A significant decrease of vascular impedance in cerebral blood vessels exists earlier than in fetal aorta or umbilical artery which could be explained by the establishent of cerebral autoregulatio n mechanisms which ensure adequate oxygen and glucose supply to embryo nic brain. There was no significant difference for RI values of luteal blood flow from the 6th to the 12th gestational week. No difference w as found between RI values of luteal blood flow in normal and ectopic pregnancy. In threatened, incomplete and missed abortions RI of luteal blood flow was significantly higher in comparison with normal pregnan cy. It seems that in the group of patients with threatened abortion, f ollow up of the luteal flow might give some prognostic value. No diffe rence in peripheral impedance and blood flow velocity of the uteroplac ental blood vessels was found between women with normal pregnancies an d women with threatened abortions and normal pregnancy outcome. There was no significant difference in terms of RI and PSV in uteroplacental blood vessels between women with threatened abortion and normal pregn ancy outcome and women with threatened abortion whose pregnancy termin ated with complete abortion and blighted ovum. In 46% of 21 women with visible retrochorionic hematoma RI in spiral arteries was higher and PSV was lower on the side of the hematoma. These values could be expla ined by compression of the wall of the spiral arteries caused by hemat oma. In missed abortion the mean RI value of the uterine artery was lo wer than the mean value in normal pregnancy, but was not in spiral art eries. Some authors reported RI values in cases of missed abortions ar ound and above the cutoff point value of 0.63. In blighted ovum RI in uterine and spiral arteries was lower in comparison to normal pregnanc y, but in the other studies this was not the case. Increased blood flo w in radial arteries in patients with pregnancy associated with uterin e myomata could be explained by higher levels of estriol hormone metab olized in the placenta. Transvaginal color Doppler could be helpful in diagnosis and differentiation of the different forms of a gestational trophoblastic disease. It seems that this technique is a good substit ute for pelvic angiography. No difference in vascular impedance of the middle cerebral artery was found between normal pregnancies and pregn ancies with vaginal bleeding. Such results could be explained by the f act that mechanisms which ensure normal blood supply to the brain in h ypoxic states become active in later pregnancy.