Fish is a really healthy food to eat, especially in pregnancy. It is rich in protein, healthy fat and minerals. It contains omega-3 fatty acids which are important for the development of the baby's central nervous system. Some women comment that they don't like fish, and ask if a fish oil supplement is a reasonable alternative. I think that if it's a supplement or nothing, then a supplement is good, but there's no substitute for the real thing, so where possible, eat fish and avoid the supplements.
Although fish is a great food source, you need to be careful about which fish you choose. Bigger fish, such as shark, eat smaller fish. They also live longer than smaller fish. Therefore, over their lifetime, they accumulate more mercury than what a smaller fish would accumulate, and this can be harmful for the developing baby when we eat bigger fish.
Small amounts of salmon or sardines every day is very beneficial to your developing baby. It does not need to be a large serve; the important thing is to have a steady stream of nutrients and fatty acids to your baby.