 The omega-3 features similar the statins to be antioxidants and anti-inflammatory drugs and their derivatives have the function of slowing the neuro-inflammation, oxidative stress and apoptotic cell death anti-inflammatory properties. Also, they have antithrombotic effects, being related to prevent disease. Studies show that supplementation with omega-3 has a positive impact on several outcomes like cardiovascular disease, asthma, rheumatoid arthritis and Alzehimer. Objective: Evaluate the relationship between supplementation of omega-3 in the dynamics of the fetal ductus arteriosus in the third trimester. Methodology: randomized double blind clinical trial. Women with gestational age between 28 to 32 weeks, literate, over 18 years will be invited. Pregnant women with anti-inflammatory drugs, they have a higher intake of dietary polyphenols to 127mg day or using drugs that may interfere with the absorption of omega-3 are excluded. The selected women will be randomized to receive capsules of omega-3 or placebo, to be consumed daily for 3 weeks. In the first interview, and after 3 weeks, they will respond the Questionnaire Food Frequency QFF to quantify polyphenols and omega 3 in their diet, weight and height will be measured and the examination of fetal echocardiography is performed. 