Magnesium sulfate and other anticonvulsants for women with pre-eclampsia

Magnesium sulfate more than halves the risk of eclampsia, and probably reduces the risk of maternal death. A quarter of women have side-effects, notably flushing. The lack of clarity on what constitutes severe pre-eclampsia may render this intervention difficult to implement. Women at low risk of pre-eclampsia may not be suitable candidates for treatment with magnesium sulfate.

RHL Commentary by Khalid S. Khan

EVIDENCE SUMMARY

This review compares the effectiveness of magnesium sulfate with other anticonvulsants among women with pre-eclampsia. There is clear evidence in favour of magnesium sulfate as it reduces the risk of eclampsia and that of maternal mortality, though the latter effect did not reach the conventional 5% level of statistical significance. The severity of pre-eclampsia where anticonvulsant treatment in this heterogeneous condition is warranted is not clear.

This review seems to be methodologically sound. However, the use of summary Number-Needed-to Treat statistic (NNT) is too simplistic. Pre-eclampsia is a heterogeneous condition with substantially different baseline risks of eclampsia in various subgroups of pregnant women (1). Hence, calculating average NNTs from pooled meta-analysis results can be seriously misleading (2). This is because NNTs are sensitive to changing baseline risk (3). The lower the risk, the higher the NNT, and the lower the expectation of benefit from anticonvulsant therapy. Conversely, the higher the baseline risk, the lower the NNT, and the higher the expectation of benefit and the more inclined the health care workers would be to recommend, and women to accept, anticonvulsant therapy. Therefore, in order to apply the results of the systematic review we require information about the benefit tailored according to variations in baseline risks, (4,5,6) and not average NNTs across all risk groups as reported in this review (see applicability of the results below).

The full RHL commentary also includes sections on:

Relevance
- Magnitude of the problem
- Applicability of the results
- Implementation of the intervention
Research
References

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This document should be cited as: Khalid S. Khan. Magnesium sulphate and other anticonvulsants for women with pre-eclampsia: RHL commentary (last revised: 8 September 2003). The WHO Reproductive Health Library, No 9, Update Software Ltd, Oxford, 2006. www.rhlibrary.com