|Methods||Randomised controlled trial.|
|Participants||135 women were randomised.|
Setting: Memphis, US.
Recruitment: March 1995 to June 1996.
Inclusion criteria: women at at least 37 weeks' gestation with blood pressure ≥ 140 mmHg systolic, ≥ 90 mmHg diastolic and/or proteinuria (≥ 300 mg per 24 hours).
Exclusion criteria: severe pre-eclampsia, fetal malpresentation, congenital anomalies, non reassuring fetal testing, contraindications to the use of magnesium sulphate,contraindications to a trial of labour.
|Interventions||Magnesium sulphate (n = 67)|
Women were given a loading infusion of 6 g magnesium sulphate over 15-20 minutes followed by a maintenance infusion of 2 g per hour continued until 12 hours postpartum.
Placebo (n = 68)
Women were given an equal volume of a saline solution by infusion.
|Outcomes||Maternal: length of labour, postpartum haemorrhage, caesarean delivery, maternal infection, maternal side effects, maternal side effects requiring treatment cessation.|
Infant: Apgar score ≤ 6 at 1 and 5 minutes, gestational age at birth.
|Notes||Participant enrolment ceased at 68% of planned enrolment following a single interim analysis.|
|Risk of bias|
|Bias||Authors' judgement||Support for judgement|
|Random sequence generation (selection bias)||Low risk||“Randomisation was performed by use of computer-generated tables of random numbers.”|
|Allocation concealment (selection bias)||Low risk||“The women and their care givers were blinded to the randomisation assignment through the use of sealed, sequentially numbered, opaque envelopes.”|
Magnesium sulphate and placebo infusions were "... dispensed by the hospital pharmacy".
|Blinding of participants and personnel (performance bias) |
|Low risk||All women and their caregivers were blind to group allocation; an identically appearing placebo infusion was used.|
|Blinding of outcome assessment (detection bias) |
|Low risk||As above.|
|Incomplete outcome data (attrition bias) |
|Low risk||No losses to follow-up were reported. No drop outs or withdrawals were reported.|
|Selective reporting (reporting bias)||Unclear risk||With no access to a trial protocol, it was not possible to determine if outcome data for all pre-specified outcomes were reported.|
|Other bias||Unclear risk||Reason for early termination of study: enrolment of women into study was terminated at 68% of planned enrolment – following a single interim analysis determining that only 37 women in each group were needed to rule out a 33% increase in the length of labour resulting from magnesium sulphate.|