Liu 2013.

Methods	Randomised controlled trial
Participants	Inclusion criteria: nulliparity; age ≥ 35 years; previous pre‐eclampsia; family history of pre‐eclampsia; multiple pregnancy; time between pregnancies ≥ 10 years; body mass index ≥ 25; diastolic pressure ≥ 80 mmHg before 20 weeks' gestation; proteinuria ≥+ on more than 1 occasion or ≥ 300 mg/24 h before 20 weeks' gestation; underlying medical conditions (pre‐existing hypertension; pre‐existing renal disease; pre‐existing diabetes; presence of antiphospholipid antibodies; chronic autoimmune disease); male sex partner's predecessor wife has previous pre‐eclampsia. The inclusion criteria include women who already have hypertension, but it may be that women that are actually recruited may not have these specific risk factors.
Interventions	This is a calcium supplement dose comparison 600 mg versus 1200 mg; it is not a placebo controlled trial.
Outcomes	Pre‐eclampsia.
Notes	This is a trial registration — the study is specifically about prevention of pre‐eclampsia — recruitment should have ended (2015) but there are no subsequent updates of the registration or publications. Awaiting assessment pending further publications.

mg: milligram
 mmHg: millimetre of mercury