As mentioned above, magnesium can relax muscles rather than forcing painful contractions. In a famous study from 1994, women in active labor had a reduced amount of magnesium in their uteruses than women who weren’t yet in labor. Boosting magnesium levels is often used to stop pre-term contractions. Women who are at risk of premature deliveries are given magnesium for this reason.
In more recent research, a 2015 study found that when mothers were given magnesium supplements during labor, it lowered the risk of fever and complications for both the woman and the baby, including protecting against “floppy baby syndrome,” where infants are born with low muscle tone.