Moving Forward
The NNTs calculated in these reviews — ranging from 44 to 63 — are convincing, and are comparable with evidence-based medicine data for prevention of other common diseases.19 For instance, the NNT for a life saved when aspirin is given immediately after a heart attack is 42. Statins given for 5 years in people with known heart disease have an NNT of 83 to save one life, an NNT of 39 to prevent one nonfatal heart attack, and an NNT of 125 to prevent one stroke. For oral anticoagulants used in nonvalvular atrial fibrillation for primary stroke prevention, the NNTs to prevent one stroke, and one death, are 22 and 42, respectively.19
In its 2010 Committee Opinion on Magnesium Sulfate Before Anticipated Preterm Birth for Neuroprotection (reaffirmed in 2020), the American College of Obstetricians and Gynecologists left it to institutions to develop their own guidelines “regarding inclusion criteria, treatment regimens, concurrent tocolysis, and monitoring in accordance with one of the larger trials.”20
Not surprisingly, most if not all hospitals have chosen a higher dose of MgSO4 administered up to 31 weeks’ gestation in keeping with the protocols employed in the NICHD-sponsored BEAM trial (See Table).
The hope moving forward is to expand treatment options for neuroprotection in cases of imminent preterm birth. Researchers have been assessing the ability of melatonin to provide neuroprotection in cases of growth restriction and neonatal asphyxia. Melatonin has anti-inflammatory and antioxidant properties and is known to mediate neuronal generation and synaptic plasticity.21
N-acetyl-L-cysteine is another potential neuroprotective agent. It acts as an antioxidant, a precursor to glutathione, and a modulator of the glutamate system and has been studied as a neuroprotective agent in cases of maternal chorioamnionitis.21 Both melatonin and N-acetyl-L-cysteine are regarded as safe in pregnancy, but much more clinical study is needed to prove their neuroprotective potential when given shortly before birth or earlier.
Dr. Burd is the Sylvan Freiman, MD Endowed Professor and Chair of the department of obstetrics, gynecology, and reproductive sciences at the University of Maryland School of Medicine, Baltimore. She has no conflicts of interest.
References
1. Clio Med. 1984;19(1-2):1-21.
2. Medicinsk Rev. (Bergen) 1906;32:264-272.
3. Am J Obstet Gynecol. 1996;174(4):1390-1391.
4. Am J Obstet Gynecol. 1959;78(1):27-32.
5. Pediatrics. 1995;95(2):263-269.
6. Am J Obstet Gynecol. 2009;201(3):279.e1-279.e8.
7. Am J Obstet Gynecol. 2010;202(3):292.e1-292.e9.
8. Pediatr Res. 2020;87(3):463-471.
9. J Child Neurol. 1992;7(1):70-76.
10. Lancet. 1997;350:1517-1518.
11. JAMA. 2003;290:2669-2676.
12. BJOG. 2007;114(3):310-318.
13. Lancet. 2002;359(9321):1877-1890.
14. N Engl J Med. 2008;359:895-905.
15. Obstet Gynecol. 2009;113(6):1327-1333.
16. Am J Obstet Gynecol. 2009;200(6):595-609.
17. Obstet Gynecol 2009;114:354-364.
18. Cochrane Database Syst Rev. 2009 Jan 21:(1):CD004661.
19. www.thennt.com.
20. Obstet Gynecol. 2010;115:669-671.
21. Front Synaptic Neurosci. 2012;13:680899.
*This story was corrected on June 10, 2024.