Yes, tamari can be substituted for soy sauce during pregnancy. Although both tamari and soy sauce differ in flavor, many people opt for tamari over soy sauce. Tamari has a stronger flavor, is less salty, and is mostly gluten-free. Many experts ask pregnant women to refrain from soy sauce, as it comprises of a lot of additives and preservatives that may be harmful during pregnancy. But tamari is known to have lesser additives although some of them have MSG. So, make sure you check the label and opt for MSG-free tamari for your stir-fries. And consult with your doctor before you use tamari in your favorite Asian delicacy.