Theobald 1937

Methods	This study was conducted at St. Mary Abbots hospital, London during 1936.
Participants	Pregnant women less than 24 weeks of gestation. No baseline characteristics comparison was performed.
Interventions	Intervention group (n = 50) received calcium lactate 20 grains, vitamin A 11,000 IU, D 450 IU. Placebo group did not receive any intervention.
Outcomes	Albuminuria + hypertension, hypertension, albuminuria, hyperemeses, oedema, headache, cramps, insomnia.
Notes	There was no proof that all the patients in intervention took capsules (vitamin A and D) and tablets (calcium lactate) regularly. Outcomes included in this study were not of review interest.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "An equal number of blue and white beads were placed in a box. Each women accepted for the experiment was asked to draw a bead from the box. Those who drew blue beads were placed in group A while those who drew white beads were placed in group B." Comment: probably done.
Allocation concealment (selection bias)	High risk	Comment: probably not done.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	No exclusion and attrition were reported.
Selective reporting (reporting bias)	Low risk	Comment: all outcomes mentioned in the methods section were presented in the paper.
Other bias	Low risk	Comment: no other bias was identified.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "participants were divided into 2 groups, the intervention group received extra vitamins and the control did not receive any intervention". Comment: probably not blinded.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "symptoms were recorded by independent antenatal officers who had no knowledge as to which patients were receiving the additional substances". Comment: outcome assessors were blinded to the treatment assignment.