In the US, women are told not to eat any raw fish like sushi. In Japan, that’s hardly the case. Still, there are concerns about mercury in some fish, as high levels of methylmercury can be toxic to your unborn baby’s nervous system. In general, the larger the fish, the more mercury it contains. So avoid tuna, mackerel, swordfish and shark, and opt for salmon, tilapia, shrimp, cod or catfish.