Omega-3 fatty acids are long-chain polyunsaturated essential fatty acids that are necessary for good health and development. Unlike omega-3 fatty acids from plant sources such as flaxseed and canola oils, fish oils and algae-derived marine oils contain the longer-chain docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids. These are called essential fatty acids because the body cannot produce them independently, so they must be consumed in adequate amounts.
The use of marine oil supplements during pregnancy has been studied as a possible strategy to prevent preterm birth (or increase gestational age) and prevent eclampsia, as well as to increase birth weight along with other potential benefits such as improving fetal brain development, and reducing the risk of cerebral palsy and postpartum depression. The theories behind the studies on birth outcomes were originally developed based on the observations of high birth weight and long gestation in communities with high fish consumption.