UTERINE ARTERY RESISTANCE INDEX (RI)

The uterine artery is visualized on a parasagittal section of the uterus at the level of the lateral margins (at the level of the bifurcation of the internal and external iliac arteries). The uterine artery passes over the internal iliac artery at its midpoint and runs upward along the uterine wall and divides into the arcuate arteries. The uterine artery is measured at its intersection with the internal iliac artery. The doppler angle must be kept below 45°.

Wk	-2SD	-1SD	Mean	+1SD	+2SD	Wk	-2SD	-1SD	Mean	+1SD	+2SD
16 17 18 19 20 21 22 23 24 25 26 27	0.43 0.42 0.41 0.40 0.39 0.38 0.38 0.37 0.36 0.36 0.35 0.35	0.49 0.48 0.48 0.47 0.46 0.45 0.44 0.44 0.43 0.42 0.42 0.41	0.56 0.55 0.54 0.53 0.53 0.52 0.51 0.50 0.50 0.49 0.49 0.48	0.63 0.62 0.61 0.60 0.59 0.59 0.58 0.57 0.56 0.56 0.55 0.55	0.69 0.68 0.68 0.67 0.66 0.65 0.64 0.64 0.63 0.62 0.62 0.61	28 29 30 31 32 33 34 35 36 37 38 39	0.34 0.34 0.33 0.33 0.32 0.32 0.32 0.31 0.31 0.31 0.31 0.31	0.41 0.40 0.40 0.39 0.39 0.39 0.38 0.38 0.38 0.38 0.37 0.37	0.47 0.47 0.46 0.46 0.46 0.45 0.45 0.45 0.44 0.44 0.44 0.44	0.54 0.54 0.53 0.53 0.52 0.52 0.52 0.51 0.51 0.51 0.51 0.51	0.61 0.60 0.60 0.59 0.59 0.59 0.58 0.58 0.58 0.58 0.57 0.57