Fiddleheads are a green vegetable harvested in the spring. They are curled young fronds of a fern. There are many varieties of ferns that grow similarly, but the ostrich and cinnamon fern are the only two that are considered edible and safe to eat.
According to health advisory by Health Canada and New York & Western Canada Centres for Disease Control and Prevention, while these fiddleheads are safe to eat, they must be properly prepared and cooked before eating. Raw fiddleheads can cause headaches, nausea, abdominal cramps, vomiting and diarrhea as they contain certain unidentified toxins and may harbour microbes.
There is no specific advisory for pregnant women on fiddle head ferns. So, go ahead and enjoy the grassy nutty flavour of this seasonal delicacy, as long as you follow the prep guidelines.