New Findings on Preterm Labor Meds: Mothers Receiving Magnesium Sulfate More Likely to have NICU Babies

A recent study due to be published in July’s "Green Journal" (Obstetrics & Gynecology Journal) found that newborns whose mothers had received magnesium sulfate were more likely to be admitted to the NICU than those whose mothers had received the alternative treatment (nifedipine). At this point, the researchers cautioned that the data did not offer a clear explanation for this finding and more research needs to be done to rule out other causes.

Deirdre Lyell, MD, a specialist in high-risk obstetrics at the Lucile S. Packard Children’s Hospital at Stanford, CA led the investigations that compared the use of magnesium sulfate with nifedipine for acute tocolysis of preterm labor.

Definitions

• Preterm labor – labor before 37 weeks of gestation (completed weeks of pregnancy).
• Preterm birth – a baby born before 37 gestation (completed weeks of pregnancy). Also called premature birth.
• Acute Tocolysis – the use of medications to delay or inhibit or stop contractions experienced during preterm labor. The medications relax overactive uterine muscles.

Main Study Findings
The researchers found magnesium sulfate was more effective in preventing delivery for 48 hours by quieting uterine contractions. But there were no significant differences in the ability of these treatments to delay delivery, in the gestational age of the newborn or in the birth weight of the infants. What was significant were the side effects experienced by each of the groups.

Two-thirds of the women on magnesium sulfate experienced mild to severe side effects including shortness of breath and fluid build-up in the lungs during the treatment. Other side effects reported with magnesium sulfate include vomiting, lethargy and blurry vision. By comparison, only one-third of the women on nifedipine experienced side effects which included headaches.

The side effects of magnesium sulfate are long remembered by the women who are on the medications. According to Dr. Lyell, "Women who have had magnesium sulfate remember it; they don't like it. Those who receive nifedipine don't feel as bad."

Take Home Message from Study
According to Dr. Lyell, there were no significant differences in relevant outcomes between the two groups studied.

What was significant, this study found, was the difference in the side effects experienced by the women, some of these were very serious.

You can read about a first hand account from Dr. Kristie McNealy on being in preterm labor and treated with both magnesium and nifedipine at the NICU 101 Blog.

First Hand Account:
McNealy K. June 29, 2007. More Side Effects with Magnesium Sulfate. NICU 101 Blog.

More Info on Preterm Labor and Preterm Birth:
March of Dimes. February 2006. Preterm Labor. Common Complications of Pregnancy. http://www.marchofdimes.com/pnhec/188_1080.asp
March of Dimes. February 2007. Preterm Birth. Quick Reference and Fact Sheet. http://www.marchofdimes.com/professionals/14332_1157.asp
Weissmiller DG. Preterm Labor. American Family Physician. 1999;59(3).
http://www.aafp.org/afp/990201ap/593.html

Sources:
Lyell DJ, Pullen K, Campbell L, Ching S, et. al. Magnesium Sulfate Compared With Nifedipine for Acute Tocolysis of Preterm Labor. Obstetrics & Gynecology. 2007;110:61-67. Abstract online at: http://www.greenjournal.org/cgi/content/abstract/110/1/61
Lucile Packard Children's Hospital. June 28, 2007. Press Release. Common Preterm Labor Drug Has More Side Effects than Alternative, Finds Study from Packard Children's Hospital and Stanford.
http://www.lpch.org/newsEvents/NewsReleases/2007/pretermLaborDrugs.html

Photo Credit: Adam Ciesielski. IV Drip - Intravenous Drug. Royalty Free Use.