Magnesium and calcium work in combination: Magnesium relaxes muscles, while calcium stimulates muscles to contract. During pregnancy, magnesium helps build and repair body tissue in both mother and fetus. A severe deficiency during pregnancy may lead to leg cramps, preeclampsia, birth defects, and infant mortality. Calcium and magnesium help regulate blood pressure and could help prevent preeclampsia. Magnesium relaxes muscles and research suggests that proper levels of magnesium during pregnancy can help keep the uterus from contracting prematurely. Magnesium helps build the baby’s strong bones and teeth and has also been known to increase the duration of sleep and improve sleep efficiency. Best Sources: Pumpkin seeds, swiss chard, spinach, sesame seeds, quinoa, black beans, sunflower seeds, cashews.