EARLY DOPPLER SONOGRAPHY OF THE UTERINE ARTERIES

Purpose: Morphological changes of the spiral arteries during the first half of pregnancy are the most important control mechanism of uterine perfusion and normal fetal nutrition. Immature development of the tro phoblast invasion in the second trimester is considered a cause for pr e-eclampsia and utero-placental insufficiency during subsequent pregna ncy. Objective: The purpose of this study was to examine flow velocity changes of the uterine arteries in uncomplicated pregnancies and to e valuate the clinical significance of pathologic Doppler flow up to the 24(th) week of gestation. Design and Methods: In a prospective study, the blood flow of both main branches of the uterine arteries was inve stigated from the 4(th) to the 24(th) week of gestation by means of tr ansvaginal Doppler flow imaging (Acuson 128 XP/10, 5.0 MHz probe and C ombison 320-5, 5.0 and 7.5 MHz probe). An average of 3 cardiac cycles was used to calculate the qualitative parameters (RI, PI, S/D ratio) a nd the flow characteristics in the early diastole (early/mid-diastolic maximal flow velocity [NIP ratio]). Normative data were obtained from 79 uncomplicated pregnancies, followed up until birth at term (mean a ge 29 years, range 18-40). The flow pattern of 25 pregnancies developi ng PIH and/or placental insufficiency were compared with the standard values (mean age 29 years, range 24-36). Results: The characteristic f low patterns in the first trimester are a high systolic peak, a distin ct diastolic ''notch'' followed by a diastolic peak, and low end-diast olic frequency shift. Until the 24(th) week, a continual increase in t hese parameters is found, with disappearance of the,,notch'' between t he 16(th) and 18(th) week. Qualitative parameters decrease steadily an d the range variations diminish at the same time, being very high in t he first trimester. We did not find any case of pathological uterine p erfusion after initial normal flow development. In cases of ensuing PI H and/or placental insufficiency, significant differences were found f rom the 16(th) week onwards. From the 22(nd) to 24(th) week, most of t he parameters were out of the 90(th) percentile, showing a sensitivity up to 100% and a specificity of 92%. From the 19(th) week onwards, th e N/P ratio had a sensitivity of 73 % and a specificity of 91%. Pathol ogical Doppler results were found on average 12 weeks before delivery in complicated pregnancies. Discussion: From the 16(th) week onwards, Doppler examination of the uterine arteries is an accurate method to d etect delayed or arrested blood flow development, which normally is co mpleted between the 20(th) and 24(th) week. The combination of qualita tive parameters such as the PI or RI, with evaluation of the early dia stolic flow (N/P ratio), seems to be best in discrimination of normal and pathologic uterine perfusion. The transvaginal method, used in our study, shows better results than the transabdominal method discribed in the literature. In conclusion, we propose a Doppler sonographic scr eening examination of the uterine arteries between the 19(th) and 22(n d) week of gestation, even if no risks are evident. In case of patholo gical results, treatment with ASS (or haemodilution?) and intensive pr enatal care is useful, after fetal anomalies with or without chromosom al aberrations have been excluded.