Seaweed is totally fine to eat during pregnancy when enjoyed in moderation.
Seaweed can be a great way to curb your salty, crunchy cravings without the need for a bag of potato chips. It’s also a great source of dietary iodine, a mineral that helps your thyroid glands create hormones needed for a number of bodily processes. This can be potentially advantageous during pregnancy, especially since your iodine needs and the demand on your thyroid gland to secrete hormones increases because your thyroid is working to support you and your baby.
The potential drawback to seaweed, however, is that the iodine content can vary. It can be quite potent in some varieties, specifically brown seaweed, and too much iodine can be a bad thing. For this reason, it's best to consume seaweed in moderation and be mindful of the type you are consuming.