Fish oils are rich sources of omega-3 fatty acids, particularly ones called DHA and EPA.  Omega-3 fatty acids contain the fatty eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), both of which are known for their anti-inflammatory properties and are very important for heart health by helping to lower triglyceride levels.  Additionally, omega-3s are responsible for the normal functioning & development of the brain, and critical for the healthy growth of the fetus in pregnant women.