There are two types of fish oil supplement - those made from the liver of the fish and those made from the body of the fish. Supplements made from the liver of the fish, such as cod liver oil, contain the retinol form of vitamin A and need to be either avoided altogether or strictly limited in pregnancy so that your daily intake does not exceed 3,300 micrograms (mcg). On the other hand, fish oils not derived from fish livers contain lots of DHA (docosahexaenoic acid), which is essential for your baby's developing eyes and brain.