In hospitals, magnesium is a life-saving drug, not a supplement

This is magnesium sulphate at monitored clinical doses through a vein; magnesium sold in capsules has never been shown to do anything for eclampsia risk. The trial ran across 33 countries with very different standards of care, so the background risk it was measured against varied from site to site. And the Cochrane review is built around this same trial, so the two are not independent of each other.

The reviewed trials establish the direction but not the size; how far the risk falls is not settled here. This is a different job from preventing a mother's seizures, working a different way, and the two should not be read as one use. And it applies to births that are very preterm, not to pregnancy generally.