['Animal data show that low protein intake in pregnancy programs higher offspring blood pressure, but similar data in humans are limited. We examined the associations of first and second trimester maternal protein intake with offspring blood pressure (BP) at the age of six months.', 'In a prospective US cohort study, called Project Viva, pregnant women completed validated semi-quantitative food-frequency questionnaires (FFQ) to measure gestational protein intake. Among 947 mother-offspring pairs with first trimester dietary data and 910 pairs with second trimester data, we measured systolic blood pressure (SBP) up to five times with an automated device in the offspring at the age of six months. Controlling for blood pressure measurement conditions, maternal and infant characteristics, we examined the effect of energy-adjusted maternal protein intake on infant SBP using multivariable mixed effects models.', 'Mean daily second trimester maternal protein intake was 17.6% of energy (mean 2111 kcal/day). First trimester nutrient intakes were similar. Mean SBP at age 6 months was 90.0 mm Hg (SD 12.9). Consistent with prior reports, adjusted SBP was 1.94 mm Hg lower [95% confidence interval (CI) -3.45 to -0.42] for each kg increase in birth weight. However, we did not find an association between maternal protein intake and infant SBP. After adjusting for covariates, the effect estimates were 0.14 mm Hg (95% CI 20.12 to 20.40) for a 1% increase in energy from protein during the second trimester, and 20.01 mm Hg (95% CI 20.24 to -0.23) for a 1% increase in energy from protein in the first trimester.'] Is maternal protein intake associated with infant blood pressure?