 The effect of anti-inflammatory substances on the dynamics of the fetal ductus arteriosus is well documented, but the anti-inflammatory property of polyunsaturated fatty acid omega-3 about changing this dynamic is not established. This study evaluate the relationship between supplementation of omega-3 in the dynamics of the fetal ductus arteriosus in the third trimester. Women with gestational between 28 to 32 weeks will receive capsules of omega-3 or placebo, to be consumed daily for 3 weeks. 