Key Points Question Is maternal intake of prenatal docosahexaenoic acid associated with reductions in childhood blood pressure? Findings In this prespecified secondary analysis of a randomized clinical trial and follow-up of 171 mothers and their offspring, the children of women randomized to receive prenatal docosahexaenoic acid did not experience an increase in systolic blood pressure and diastolic blood pressure if they became overweight or obese compared with children of women randomized to placebo. A statistically significant interaction was found between prenatal treatment and child weight status. Meaning Docosahexaenoic acid intake during pregnancy may protect children from the blood pressure–elevating consequence of childhood overweight condition or obesity.