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

OBJECTIVES: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.