No information is available on the clinical use of magnesium oxide during breastfeeding. However, other magnesium salts have been studied. A study on the use of magnesium hydroxide during breastfeeding found no adverse reactions in breastfed infants. Intravenous magnesium increases milk magnesium concentrations only slightly. Oral absorption of magnesium by the infant is poor, so maternal magnesium hydroxide is not expected to affect the breastfed infant's serum magnesium. Magnesium oxide supplementation during pregnancy might delay the onset of lactation, but it can be taken during breastfeeding and no special precautions are required.