We assessed the effect of using customized birth-weight standards on the association of uterine artery Doppler resistance index (RI) and birth weight. This was a cross-sectional study of 2035 pregnancies scanned at 19 to 23 weeks. Both uterine arteries were identified using color flow mapping, and the RI was measured. The pregnancy outcome was obtained from the delivery suite database and the customized birth-weight centile calculated for each pregnancy. Both birth-weight and customized birth-weight centiles were converted to z-scores. The correlation of uterine artery RI with birth weight was examined using conventional and customized birth-weight standards. Conventional and customized birth weights showed a significant correlation with uterine artery RI ( R = -0.062 and -0.208, respectively). The correlation was significantly improved by the use of customized birth weight. Use of customized birth weight significantly improves the correlation of uterine artery RI and birth weight. This finding may partly explain the lower sensitivity of uterine artery Doppler screening for fetal growth restriction as compared with preeclampsia.