Supplements made from the liver of the fish, such as cod liver oil, contain the retinol form of vitamin A and need to be avoided altogether during pregnancy. However, fish oils not derived from fish livers contain lots of DHA (docosahexaenoic acid), an omega-3 essential fatty acid which is essential for your baby's developing eyes and brain. At present, there is no recommended daily intake of DHA, although this is currently being researched.
Source from Babycentre
Fish oil supplements during pregnancy