Magnesium Sulfate for Preterm Labor Is Ineffective

September 8, 2014

Magnesium sulfate has its uses, but it's ineffective for delaying or preventing preterm birth; also, using it as a tocolytic could spell trouble for baby.

Giving magnesium sulfate to women in preterm labor does not prevent babies from being born, a recent meta-analysis found. Although this isn't breaking news, this analysis looked at women in which magnesium sulfate was the only tocolytic given and compared them with women who received other treatment options, including other tocolytics, but not magnesium sulfate.

Pertinent Points

- Magnesium sulfate does not prevent preterm birth and does not prevent health problems in the infants, a Cochrane analysis found.

- The analysis looked at 37 trials and consistently found that the drug had no benefit to the mother or child when given to stop preterm labor.

- The exception: when the drug was given to women with preeclampsia or to protect babies’ brains.

In addition, magnesium sulfate failed to prevent other serious health issues in babies. In fact, the analysis found that use of magnesium sulfate as a tocolytic agent, when compared with placebo or no treatment, may even be associated with an increased risk of total fetal, neonatal, or infant mortality (risk ratio, 4.56; 95% CI, 1.00 to 20.86; n=257 babies), although this borderline finding requires more study. However, antenatal magnesium sulfate remains effective in helping women with preeclampsia and for helping to protect babies' brains.

The meta-analysis, conducted by the Cochrane Pregnancy and Childbirth Group and published online last month, looked at 37 trials for a total of 3,571 pregnant women who went into labor prior to 37 weeks' gestation.

Women who were given magnesium sulfate in an attempt to stop the uterus from contracting were no less likely to deliver their babies within 48 hours than women who did not get the drug. Among the trials, the control group did not receive magnesium sulfate but did receive a number of different treatment options, including placebo, no alternative, calcium channel blockers, and COX inhibitors, among others.

Similarly, when trials sought to determine the effect of the drug on outcomes for infants, the trials consistently showed that there was no difference between babies exposed to magnesium sulfate and unexposed infants. Also, when it came to infant deaths and fetal deaths, the combined trial results showed no differences between infants exposed to magnesium sulfate and those not exposed.

While the trials focused on preterm births, no trials looked at the drugs use in extremely preterm birth.