The Basics
What is Magnesium Sulfate?
Used to prevent and treat low amounts of magnesium in the blood. Some brands are also used to treat stomach upset, heartburn, and acid indigestion.
Brand names for Magnesium Sulfate
Magnesium Sulfate
How Magnesium Sulfate is classified
Anti-Arrhythmia Agents, Anticonvulsants, Cathartics, Gastrointestinal Agents, Magnesium Compounds, Tocolytic Agents
Magnesium Sulfate During Pregnancy
Magnesium Sulfate pregnancy category
Category CNote that the FDA has deprecated the use of pregnancy categories, so for some medications, this information isn’t available. We still think it’s useful to list historical info, however, given what a common proxy this has been in the past.
What we know about taking Magnesium Sulfate while pregnant
Animal reproduction studies have not been conducted with Magnesium Sulfate Injection, USP 50%. It is also not known whether Magnesium Sulfate Injection, USP 50% can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Magnesium Sulfate Injection, USP 50% should be given to a pregnant woman only if clearly needed.
Taking Magnesium Sulfate While Breastfeeding
What are recommendations for lactation if you're taking Magnesium Sulfate?
Intravenous magnesium increases milk magnesium concentrations only slightly and oral absorption of magnesium by the infant is poor, so maternal magnesium therapy is not expected to affect the breastfed infant’s serum magnesium. Although intravenous magnesium sulfate given prior to delivery might affect the infant’s ability to breastfeed, intention to breastfeed may be a more important determinant of breastfeeding initiation.[1] Postpartum use of intravenous magnesium sulfate for longer than 6 hours appears to delay the onset of lactation.[2][3]
Maternal / infant drug levels
Intravenous magnesium increases milk magnesium concentrations only slightly and oral absorption of magnesium by the infant is poor, so maternal magnesium therapy is not expected to affect the breastfed infant’s serum magnesium. Although intravenous magnesium sulfate given prior to delivery might affect the infant’s ability to breastfeed, intention to breastfeed may be a more important determinant of breastfeeding initiation.[1] Postpartum use of intravenous magnesium sulfate for longer than 6 hours appears to delay the onset of lactation.[2][3]
Possible effects of Magnesium Sulfate on milk supply
One mother who received intravenous magnesium sulfate for 3 days for pregnancy-induced hypertension had lactogenesis II delayed until day 10 postpartum. No other specific cause was found for the delay, although a complete work-up was not done.[6] A subsequent controlled clinical trial found no evidence of delayed lactation in mothers who received intravenous magnesium sulfate therapy.[7] Some, but not all, studies have found a trend toward increased time to the first feeding or decreased sucking in infants of mothers treated with intravenous magnesium sulfate during labor because of placental transfer of magnesium to the fetus.[7][8] Another study found that among women with severe pre-eclampsia who received intravenous magnesium sulfate for up to one day postpartum and who intended to breastfeed, 85% of infants receiving routine well-baby care and 69% of those admitted to the NICU, breastfeeding was successfully initiated.[1]
A study randomized women with preeclampsia to receive intravenous magnesium sulfate for either 6 or 24 hours postpartum. There was no difference in the rate of eclampsia between the two groups. However, those who received the infusion for 24 hours had a delayed onset of lactation, 36.5 hours compared with 25.7 hours in the 6-hour group.[2]
A prospective, multicenter, randomized, controlled trial in 9 Latin American maternity hospitals compared patients with severe pre-eclampsia who had received at least 8 grams of magnesium sulfate prior to placebo. Patients were randomized to continue magnesium sulfate for 24 hours postpartum (n = 555) or stopping the infusion (n = 558). The time to lactation was significantly delayed in those who received magnesium sulfate postpartum (24.1 vs. 17.1 hours).[3]
Possible alternatives to Magnesium Sulfate
(Laxative) Docusate, Magnesium Hydroxide, Psyllium, Sodium Picosulfate, Sodium Phosphate.
List of References
Lactation sources: Drugs and Lactation Database (LactMed) [Internet]. Bethesda (MD): National Library of Medicine (US); 2006-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK501922/1. Cordero L, Valentine CJ, Samuels P et al. Breastfeeding in women with severe preeclampsia. Breastfeed Med. 2012;7:457-63. PMID: 22871169
2. Vigil-De Gracia P, Ramirez R, Duran Y et al. Magnesium sulfate for 6 vs 24 hours post delivery in patients who received magnesium sulfate for less than 8 hours before birth: A randomized clinical trial. BMC Pregnancy Childbirth. 2017;17:241. PMID: 28738788
3. Vigil-De Gracia P, Ludmir J, Ng J et al. Is there benefit to continue magnesium sulfate post-partum in women receiving magnesium sulfate prior to delivery? A randomized controlled study. BJOG. 2018;125:1304-11. PMID: 29878650
4. Cruikshank DP, Varner MW, Pitkin RM. Breast milk magnesium and calcium concentrations following magnesium sulfate treatment. Am J Obstet Gynecol. 1982;143:685-8. PMID: 7091241
5. Baldwin WF. Clinical study of senna administration to nursing mothers.:assessment of effects on infant bowel habits. Can Med Assoc J. 1963;89:566-7. PMID: 14045350
6. Haldeman W. Can magnesium sulfate therapy impact lactogenesis? J Hum Lact. 1993;9:249-52. PMID: 8260059
7. Riaz M, Porat R et al. The effects of maternal magnesium sulfate treatment on newborns: a prospective controlled study. J Perinatol. 1998;18:449-54. PMID: 9848759
8. Rasch DK, Huber PA et al. Neurobehavioral effects of neonatal hypermagnesemia. J Pediatr. 1982;100:272-6. PMID: 7199083
Disclaimer: This material is provided for educational purposes only and is not intended for medical advice, diagnosis, or treatment. Consult your healthcare provider with any questions.
