During pregnancy, omega 3 supplementation has raised its popularity due to evidence that it would show not only benefits in the neural and visual development of the unborn child, but also in the prevention of obstetrical pathologies associated with of perinatal morbidity and mortality. Omega 3 polyunsaturated fatty acids (PUFAs), specifically, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), possess anti-inflammatory, vasodilatory and anti-aggregating properties, which have led to the use of PUFAs in the prevention of cardiovascular diseases. In this review, we detail the effects of omega 3 supplementation on different aspects of pregnancy such as prevention of preterm birth, pre-eclampsia, postpartum depression, and improved metabolism during gestational diabetes. Although there are several randomized clinical trials using omega-3 supplementation during pregnancy, the evidence remains inconclusive, due to variability in dosage and administration time. Certainly, a greater number of high-quality studies including randomized clinical trials are necessary to determine the impact of omega 3 supplementation during pregnancy in the prevention of obstetric pathologies.