© 2014 Informa UK Ltd. Objective: The anti-oxidant and proangiogenic protein haptoglobin (Hp) is believed to be important for implantation and pregnancy, although its specific role is not known. The three phenotypes (1-1, 2-1 and 2-2) differ in structure and function. Hp 2-2 is associated with increased vascular stiffness in other populations. We examined whether Hp phenotype is associated with abnormal uterine artery Doppler (UAD) in pregnancy. Methods: We conducted a secondary analysis of a preeclampsia prediction cohort nested within a larger placebo-controlled randomized clinical trial of antioxidants for prevention of preeclampsia. We determined Hp phenotype in 2184 women who completed UAD assessments at 17 weeks gestation. Women with notching were re-evaluated for persistent notching at 24 weeks' gestation. Logistic regression was used to assess differences in UAD indices between phenotype groups. Results: Hp phenotype did not significantly influence the odds of having any notch (p = 0.32), bilateral notches (p = 0.72), or a resistance index (p = 0.28) or pulsatility index (p = 0.67) above the 90th percentile at 17 weeks' gestation. Hp phenotype also did not influence the odds of persistent notching at 24 weeks (p = 0.25). Conclusions: Hp phenotype is not associated with abnormal UAD at 17 weeks' gestation or with persistent notching at 24 weeks.