# Magnesium sulfate to prevent and treat eclampsia

Intervention · id `maternal:magnesium-sulfate-eclampsia` · Maternal & Newborn Atlas · release `c7fb95f1d15a7d13` (public)

> General information from published sources, not medical advice, and not reviewed by clinicians. Check the cited source before relying on anything here.

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Browse, life stage: Pregnancy; Childbirth; Postpartum  
Browse, care area: Pregnancy conditions  

## In plain language

Magnesium sulfate is a medicine given by injection or drip to women with pre-eclampsia to lower the chance of a seizure, and to women who have had a seizure to stop more. In the Magpie trial it cut seizures in women with pre-eclampsia by more than half. In the Collaborative Eclampsia Trial it worked better than diazepam or phenytoin at stopping repeat seizures. It also caused side-effects, and it did not clearly change the risk of the baby dying.

## Technical summary

Medicine strategy for eclampsia and pre-eclampsia, kept apart from magnesium sulfate for the baby's brain protection before early preterm birth, which is a different use recorded elsewhere in this atlas; evidence for one use does not apply to the other. Two claims sit here: the Collaborative Eclampsia Trial (treatment of eclampsia against diazepam and phenytoin) and the Magpie trial (prevention of eclampsia against placebo, with a separate claim on death of the baby). Dose and route are not given in the abstracts and are not recorded. Sources are PubMed abstracts only.

## Claims, with the population each applies to

## Context: Women with eclampsia in the Collaborative Eclampsia Trial (1995)

Recipient: Maternal; Population: Women with eclampsia, a seizure in association with pre-eclampsia, recruited into an international multicentre randomised trial that compared standard anticonvulsant regimens. 1687 women were recruited; data are available for 1680 (453 allocated magnesium sulphate against 452 allocated diazepam, and 388 allocated magnesium sulphate against 387 allocated phenytoin). Use this context only for the maternal outcomes of these comparisons.; Care setting: Not stated in the source; Geography: International; the abstract does not name the countries; Life stage: Pregnancy, labour or after birth; the abstract does not say when the seizure occurred; Gestational age: Not reported; Postnatal age: Not reported; Follow-up: Follow-up is not given in the abstract.

### The Collaborative Eclampsia Trial randomly compared anticonvulsants in 1687 women with eclampsia. Women allocated magnesium sulphate had a 52% lower risk of recurrent convulsions than those allocated diazepam (60 of 453 women, 13.2%, against 126 of 452, 27.9%; 95% CI 64% to 37% reduction), and a 67% lower risk than those allocated phenytoin (22 of 388, 5.7%, against 66 of 387, 17.1%; 95% CI 79% to 47% reduction). Maternal mortality was non-significantly lower with magnesium sulphate in both comparisons. The authors conclude there is compelling evidence in favour of magnesium sulphate, rather than diazepam or phenytoin, for the treatment of eclampsia.

- Category: Effect
- Evidence stage: Interventional
- Certainty: Certainty not assessed
- Applies to: Recipient: Maternal; Population: Women with eclampsia, a seizure in association with pre-eclampsia, recruited into an international multicentre randomised trial that compared standard anticonvulsant regimens. 1687 women were recruited; data are available for 1680 (453 allocated magnesium sulphate against 452 allocated diazepam, and 388 allocated magnesium sulphate against 387 allocated phenytoin). Use this context only for the maternal outcomes of these comparisons.; Care setting: Not stated in the source; Geography: International; the abstract does not name the countries; Life stage: Pregnancy, labour or after birth; the abstract does not say when the seizure occurred; Gestational age: Not reported; Postnatal age: Not reported; Follow-up: Follow-up is not given in the abstract.
- Limitations: The comparison is magnesium sulphate against diazepam and against phenytoin in women who already had eclampsia; there was no placebo group, and the result is about treating seizures, not preventing them (the Magpie claim is about prevention in pre-eclampsia). The trial dates from 1995. PubMed lists a published erratum (Lancet 1995;346:258) that has no PubMed record and was not read. The abstract also reports outcomes for the babies of the women allocated magnesium sulphate before delivery, which belong to a newborn context and are not summarised here. Only the abstract was read.
- Last checked: 2026-10-14
- Source problem: a cited source is corrected. Check the sources before relying on this claim.
- Sources:
  1. Supports: Which anticonvulsant for women with eclampsia? Evidence from the Collaborative Eclampsia Trial (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched. PubMed lists a published erratum (Lancet 1995;346:258) that has no PubMed record and was not read; the snapshot is marked corrected because of that erratum, whose content is not known.) <https://pubmed.ncbi.nlm.nih.gov/7769899/>
     Locator: Abstract, sentences 3 to 5: design and numbers analysed. Retrieved 2026-10-14T18:19:22Z. Source state: Corrected. Snapshot hash: d51443591607df5b330709effbd6b72aa681fd190e5e8e62ce475473e8dc6e14.
     How it applies: PubMed abstract.
  2. Supports: Which anticonvulsant for women with eclampsia? Evidence from the Collaborative Eclampsia Trial (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched. PubMed lists a published erratum (Lancet 1995;346:258) that has no PubMed record and was not read; the snapshot is marked corrected because of that erratum, whose content is not known.) <https://pubmed.ncbi.nlm.nih.gov/7769899/>
     Locator: Abstract, sentences 7 to 11: recurrent convulsions and maternal mortality. Retrieved 2026-10-14T18:19:22Z. Source state: Corrected. Snapshot hash: d51443591607df5b330709effbd6b72aa681fd190e5e8e62ce475473e8dc6e14.
     How it applies: PubMed abstract.
  3. Supports: Which anticonvulsant for women with eclampsia? Evidence from the Collaborative Eclampsia Trial (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched. PubMed lists a published erratum (Lancet 1995;346:258) that has no PubMed record and was not read; the snapshot is marked corrected because of that erratum, whose content is not known.) <https://pubmed.ncbi.nlm.nih.gov/7769899/>
     Locator: Abstract, sentence 14: authors' conclusion. Retrieved 2026-10-14T18:19:22Z. Source state: Corrected. Snapshot hash: d51443591607df5b330709effbd6b72aa681fd190e5e8e62ce475473e8dc6e14.
     How it applies: PubMed abstract.
  4. Background: Which anticonvulsant for women with eclampsia? Evidence from the Collaborative Eclampsia Trial (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched. PubMed lists a published erratum (Lancet 1995;346:258) that has no PubMed record and was not read; the snapshot is marked corrected because of that erratum, whose content is not known.) <https://pubmed.ncbi.nlm.nih.gov/7769899/>
     Locator: Abstract, sentence 13: babies' outcomes (not summarised). Retrieved 2026-10-14T18:19:22Z. Source state: Corrected. Snapshot hash: d51443591607df5b330709effbd6b72aa681fd190e5e8e62ce475473e8dc6e14.
     How it applies: PubMed abstract.

## Context: Babies of women with pre-eclampsia randomised before delivery (Magpie)

Recipient: Mixed recipients; Population: The babies of women who were randomised before delivery, counted from the time of randomisation, so fetal and newborn deaths are counted together as death of the baby. Use this context only for that outcome.; Care setting: Not stated in the source; Geography: 33 countries; the abstract does not name them; Life stage: Pregnancy, until birth, and the newborn period; Gestational age: Not reported; Postnatal age: Not reported; Follow-up: Follow-up was until discharge from hospital after delivery.

### For women randomised before delivery in the Magpie trial, there was no clear difference in the risk of the baby dying: 576 babies (12.7%) in the magnesium sulphate group against 558 (12.4%) in the placebo group (relative risk 1.02, 99% CI 0.92 to 1.14). Death of the baby was a primary outcome of the trial, alongside eclampsia.

- Category: Effect
- Evidence stage: Interventional
- Certainty: Certainty not assessed
- Applies to: Recipient: Mixed recipients; Population: The babies of women who were randomised before delivery, counted from the time of randomisation, so fetal and newborn deaths are counted together as death of the baby. Use this context only for that outcome.; Care setting: Not stated in the source; Geography: 33 countries; the abstract does not name them; Life stage: Pregnancy, until birth, and the newborn period; Gestational age: Not reported; Postnatal age: Not reported; Follow-up: Follow-up was until discharge from hospital after delivery.
- Limitations: This is a null result as reported, for the babies of women randomised before delivery. The abstract gives the number of deaths and percentages but no denominators, so none are computed. The result says nothing about magnesium sulfate given to women for fetal protection before early preterm birth, which is a separate use with its own trial evidence in another record. Only the PubMed abstract was read.
- Last checked: 2026-10-14
- Sources:
  1. Supports: Do women with pre-eclampsia, and their babies, benefit from magnesium sulphate? The Magpie Trial: a randomised placebo-controlled trial (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1016/s0140-6736(02)08778-0>
     Locator: Abstract, METHODS, sentences 2 and 3: groups and primary outcomes. Retrieved 2026-10-14T18:18:28Z. Source state: Current. Snapshot hash: 89dad4b9c1c1e96396fa90fbd58c8272b6eb3891a7f0b73066a9a511183cf19d.
     How it applies: PubMed abstract.
  2. Supports: Do women with pre-eclampsia, and their babies, benefit from magnesium sulphate? The Magpie Trial: a randomised placebo-controlled trial (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1016/s0140-6736(02)08778-0>
     Locator: Abstract, FINDINGS, sentence 5: death of the baby. Retrieved 2026-10-14T18:18:28Z. Source state: Current. Snapshot hash: 89dad4b9c1c1e96396fa90fbd58c8272b6eb3891a7f0b73066a9a511183cf19d.
     How it applies: PubMed abstract.

## Context: Women with pre-eclampsia who had not given birth or were within 24 hours after birth (Magpie)

Recipient: Maternal; Population: Women with pre-eclampsia, defined by blood pressure of 140/90 mm Hg or more and proteinuria of 1+ (30 mg/dL) or more, who had not given birth or were 24 hours or less postpartum, and for whom there was clinical uncertainty about magnesium sulphate. Randomised in 33 countries. Use this context for the maternal outcomes eclampsia and maternal death.; Care setting: Not stated in the source; Geography: 33 countries; the abstract does not name them; Life stage: Pregnancy or up to 24 hours after birth; Gestational age: Not reported; Postnatal age: Not reported; Follow-up: Follow-up was until discharge from hospital after delivery.

### In the Magpie trial, 10,141 women with pre-eclampsia who had not given birth or were within 24 hours after birth were randomised in 33 countries to magnesium sulphate (5071 women) or placebo (5070 women). Women allocated magnesium sulphate had a 58% lower risk of eclampsia (95% CI 40 to 71) than those allocated placebo (40 women, 0.8%, against 96, 1.9%; 11 fewer women with eclampsia per 1000 women). Maternal mortality was also lower with magnesium sulphate, with a wide interval that includes no effect (relative risk 0.55, 0.26 to 1.14). Side-effects were reported by 1201 of 4999 women (24%) given magnesium sulphate against 228 of 4993 (5%) given placebo. The authors conclude there do not appear to be substantive harmful effects to mother or baby in the short term.

- Category: Effect
- Evidence stage: Interventional
- Certainty: Certainty not assessed
- Applies to: Recipient: Maternal; Population: Women with pre-eclampsia, defined by blood pressure of 140/90 mm Hg or more and proteinuria of 1+ (30 mg/dL) or more, who had not given birth or were 24 hours or less postpartum, and for whom there was clinical uncertainty about magnesium sulphate. Randomised in 33 countries. Use this context for the maternal outcomes eclampsia and maternal death.; Care setting: Not stated in the source; Geography: 33 countries; the abstract does not name them; Life stage: Pregnancy or up to 24 hours after birth; Gestational age: Not reported; Postnatal age: Not reported; Follow-up: Follow-up was until discharge from hospital after delivery.
- Limitations: The authors' summary that magnesium sulphate probably reduces the risk of maternal death rests on a relative risk whose interval includes no effect. The only notable difference in maternal or neonatal morbidity was for placental abruption (relative risk 0.67, 99% CI 0.45 to 0.89); other morbidity was not summarised. This claim is about the women. Death of the baby is a separate claim and a separate context. Only the PubMed abstract was read; the full text and the registry record were not. The ISRCTN number is not used because the PubMed record does not print it.
- Last checked: 2026-10-14
- Sources:
  1. Supports: Do women with pre-eclampsia, and their babies, benefit from magnesium sulphate? The Magpie Trial: a randomised placebo-controlled trial (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1016/s0140-6736(02)08778-0>
     Locator: Abstract, METHODS: population, groups and primary outcomes. Retrieved 2026-10-14T18:18:28Z. Source state: Current. Snapshot hash: 89dad4b9c1c1e96396fa90fbd58c8272b6eb3891a7f0b73066a9a511183cf19d.
     How it applies: PubMed abstract.
  2. Supports: Do women with pre-eclampsia, and their babies, benefit from magnesium sulphate? The Magpie Trial: a randomised placebo-controlled trial (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1016/s0140-6736(02)08778-0>
     Locator: Abstract, FINDINGS, sentences 2 to 4 and 6: side-effects, eclampsia, maternal mortality, other morbidity. Retrieved 2026-10-14T18:18:28Z. Source state: Current. Snapshot hash: 89dad4b9c1c1e96396fa90fbd58c8272b6eb3891a7f0b73066a9a511183cf19d.
     How it applies: PubMed abstract.
  3. Supports: Do women with pre-eclampsia, and their babies, benefit from magnesium sulphate? The Magpie Trial: a randomised placebo-controlled trial (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities. The full text and the version of record were not fetched.) <https://doi.org/10.1016/s0140-6736(02)08778-0>
     Locator: Abstract, INTERPRETATION, sentence 2. Retrieved 2026-10-14T18:18:28Z. Source state: Current. Snapshot hash: 89dad4b9c1c1e96396fa90fbd58c8272b6eb3891a7f0b73066a9a511183cf19d.
     How it applies: PubMed abstract.

## Connected pages

- Collaborative Eclampsia Trial comparison of anticonvulsants in women with eclampsia: Eclampsia (mother) (`maternal:eclampsia`) [a claim, not a settled fact; see claim `maternal:claim-collaborative-eclampsia-trial` and its context]
- Magpie: effect on the risk of eclampsia in women with pre-eclampsia: Pre-eclampsia (`maternal:preeclampsia`) [a claim, not a settled fact; see claim `maternal:claim-magpie-eclampsia` and its context]
- Filed under this front: Medicines and vaccines (`maternal:front-medicines-and-vaccines`)
- Related to: Magnesium sulfate (`maternal:magnesium-sulfate`)
- Related to: Magnesium sulfate before very preterm birth to protect the baby's brain (`maternal:magnesium-sulfate-fetal-neuroprotection`)
- Investigated in: Magpie trial (magnesium sulfate in pre-eclampsia) (`maternal:magpie-trial`)

## Provenance

Content hash: f001231f39265f008aa2d5571473eafe5c8f9379cc94c85b56c3bfbcf89ffc7d
Last substantive edit: 2026-10-14
Evidence last checked: 2026-10-14