Prospective evaluation of renal artery resistance and pulsatility indices in normal pregnant women.

Abstract

To establish normal values for renal artery resistance index (RI) and pulsatility index (PI) during gestation and, by comparison with non-pregnant controls, to determine if pregnancy affects these indices. This was a prospective longitudinal study involving 36 normal pregnant women who underwent a total of 280 examinations at 4-week intervals from the 6th gestational week to the end of pregnancy. High-resolution ultrasound equipment with 'triplex' Doppler facilities was used. RI and PI were obtained for the main arteries of both kidneys. The same evaluation was performed in 15 non-pregnant women as controls. The mean RI in pregnant and non-pregnant women was the same (0.65 +/- 0.03 for controls and 0.65 +/- 0.02 for the pregnant women). For PI, the values were 1.25 +/- 0.12 for non-pregnant women and 1.18 +/- 0.09 for pregnant women. The only statistical difference (P < 0.05) was found between the PI of the left renal artery in the control group (1.29 +/- 0.20) and that in the pregnant group at the 8-12-week interval of gestational age (1.08 +/- 0.14). No significant alterations in renal artery RI and PI occur during normal pregnancy, except for in a subgroup of patients between 8 and 12 weeks of gestation.