Velocidade sistólica máxima e índice de resistência de artérias fetais durante a segunda metade da gestação Peak systolic velocity and resistance index of fetal arteries during the second half of pregnancy

Purpose: to assess peak systolic velocity (PSV) and the resistance index (RI) in the middle cerebral artery (MCA), suprarenal aorta (SRA) and infrarenal aorta (IRA) of the fetus and in the umbilical artery (UA) between the 22nd and 38th week of gestation. Methods: a prospective study which evaluated the parameters of 33 normal fetuses in the 22 nd , 26th, 30 th , and 38th week of gestation. Pregnant women with a singleton fetus with no diseases or complications and who agreed to participate were included in the study. Exclusion criteria were fetal malformations, discontinuation of prenatal care visits and mothers who smoked, used alcohol or illicit drugs. Ultrasound examinations were performed by a single observer. For the acquisition of the Doppler velocimetry tracing in the MCA, SRA, IRA and UA, the sample volume was 1 to 2 mm, placed in the center of the arteries. The insonation angle was 5 o to 19 o in the MCA, below 45 o in the SRA and IRA, and less than 60 o in the UA. We used a wall filter of 50-100 Hz. The parameters were calculated automatically with the frozen image, three measurements being made. The final result was obtained by the arithmetic mean of the three values. Data were analyzed by analysis of