During pregnancy, women must take care to food, both for their own health and the unborn baby's health. Since the mother is the only source of nutrients to the fetus, she needs a balanced diet which should include Omega-3 fatty acids daily dose.
Even after birth the mother needs a balanced diet as she will breastfeed. Indeed, before, during and after pregnancy DHA-rich foods should definitely be part of healthy nutrition of the mother, both for its health as well as child health.