"Magnesium is an important nutrient that helps relax muscles and build strong bones and teeth in your baby to be! Not only can adequate magnesium help you rest a little easier at night, it can also help with the inevitable constipation that can result from pregnancy," says Shaw. It's a win-win for both mom and baby. The RDA is set at 360 mg per day, she says, so make sure you're eating plenty of nuts and seeds, avocado, leafy greens, and fortified grains.