Am Fam Physician. 2010 Dec 1;82(11):1310-1312.
Original Article: Preterm Labor
Issue Date: February 15, 2010
Available at: http://www.aafp.org/afp/2010/0215/p477.html
to the editor: I appreciated Dr. Sayres' thoughtful review on preterm labor. However, the role of magnesium sulfate in the management of preterm labor deserves further comment. As Dr. Sayres noted, a 2002 Cochrane systematic review concluded that magnesium sulfate is ineffective in tocolysis1; it is therefore no longer recommended for routine use as a tocolytic.2 In contrast, physicians should consider antenatal use of magnesium sulfate in women with threatened preterm birth to reduce the infant's risk of cerebral palsy.
Cerebral palsy disproportionately affects preterm infants, with an incidence of 4 to 8 percent among infants with a very low birth weight.3 Researchers have postulated that magnesium sulfate might protect the infant brain from cerebral palsy by assisting in glutamate homeostasis; by causing vasodilation, which leads to increased cerebral blood flow; or by reducing free radicals.3 At least five prospective, randomized controlled trials have examined the use of magnesium sulfate specifically for the prevention of cerebral palsy in preterm infants.4 A recent Cochrane systematic review (n = 6,145 infants) found that infants exposed to antenatal magnesium sulfate had a significantly lower risk of cerebral palsy (relative risk = 0.68; 95% confidence interval, 0.54 to 0.87).4 No statistically significant effect on infant mortality was detected (relative risk = 1.04; 95% confidence interval, 0.92 to 1.17), nor were there any significant effects on major maternal complications.
Based on these findings, some tertiary care centers have instituted protocols for neuroprophylaxis in women with threatened preterm delivery at 32 weeks' gestation or less. One protocol involves a 6-g loading dose over 20 to 30 minutes, followed by an infusion of 2 g per hour for up to 12 hours, at which point the risk of imminent delivery is reassessed and the infusion discontinued, if indicated.5
Further study may reveal the optimal dosage of magnesium sulfate and its specific risks and benefits for infants at 32 to 34 weeks' gestation. Until such a dosage is determined, family physicians—in consultation with obstetrician-gynecologists or perinatologists, if local practice patterns dictate—should consider using magnesium sulfate in appropriately selected patients.
Author disclosure: Nothing to disclose.
REFERENCESshow all references
1. Crowther CA, Hiller JE, Doyle LW. Magnesium sulphate for preventing preterm birth in threatened preterm labour. Cochrane Database Syst Rev. 2002;(4):CD001060....
2. Grimes DA, Nanda K. Magnesium sulfate tocolysis: time to quit. Obstet Gynecol. 2006;108(4):986–989.
3. Cahill AG, Caughey AB. Magnesium for neuroprophylaxis: fact or fiction? Am J Obstet Gynecol. 2009;200(6):590–594.
4. Doyle LW, Crowther CA, Middleton P, Marret S, Rouse D. Magnesium sulphate for women at risk of preterm birth for neuroprotection of the fetus. Cochrane Database Syst Rev. 2009;(1):CD004661.
5. Rouse DJ. Magnesium sulfate for the prevention of cerebral palsy. Am J Obstet Gynecol. 2009;200(6):610–612.
in reply: I would like to thank Dr. Garrison for his thoughtful letter raising the issue of magnesium sulfate neuroprophylaxis in the context of preterm labor. A recent committee opinion from the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine (ACOG/SMFM)1 also gives tentative support for the use of magnesium sulfate for fetal neuroprotection in preterm labor. I agree with the ACOG/SMFM recommendation that individual centers “develop specific guidelines regarding inclusion criteria, treatment regimens, concurrent tocolysis, and monitoring in accordance with one of the larger trials.”1
Author disclosure: Nothing to disclose.
1. American College of Obstetricians and Gynecologists Committee on Obstetric Practice; Society for Maternal-Fetal Medicine. Committee Opinion No. 455: Magnesium sulfate before anticipated preterm birth for neuroprotection. Obstet Gynecol. 2010;115(3):669–671.
Send letters to Kenneth W. Lin, MD, MPH, Associate Deputy Editor for AFP Online, e-mail: email@example.com, or 11400 Tomahawk Creek Pkwy., Leawood, KS 66211-2680.
Please include your complete address, e-mail address, and telephone number. Letters should be fewer than 400 words and limited to six references, one table or figure, and three authors.
Letters submitted for publication in AFP must not be submitted to any other publication. Possible conflicts of interest must be disclosed at time of submission. Submission of a letter will be construed as granting the American Academy of Family Physicians permission to publish the letter in any of its publications in any form. The editors may edit letters to meet style and space requirements.
Copyright © 2010 by the American Academy of Family Physicians.
This content is owned by the AAFP. A person viewing it online may make one printout of the material and may use that printout only for his or her personal, non-commercial reference. This material may not otherwise be downloaded, copied, printed, stored, transmitted or reproduced in any medium, whether now known or later invented, except as authorized in writing by the AAFP. Contact firstname.lastname@example.org for copyright questions and/or permission requests.
Want to use this article elsewhere? Get Permissions