Table 1.
Features of the included studies
| Study | Methods | Participants | Interventions included in this review | Risk of bias |
|---|---|---|---|---|
| Almirante (1998)16 | ‘divided into two groups and followed up until delivery’ | 430 nulliparous pregnant women who were adolescents and elderly (High risk of pre-eclampsia) | 500 mg elemental calcium from 16 to 20 weeks till delivery versus controls | High |
| Bassaw (1998)15 | Randomisation using a table of random numbers, supplements were distributed in sealed envelopes. | Pregnant women recruited before 20 weeks of gestation, primigravidae, or multigravidae with obstetric history of pre-eclampsia. No underlying medical disorders. (High risk of pre-eclampsia). Setting: Trinidad, women of African, East Indian and mixed ethnicity. | Included in this review: 600 mg elemental calcium plus 80 mg aspirin daily versus 80 mg aspirin (other groups studied were control and high-dose calcium alone). | Low |
| Cong (1995)17 | ‘randomised and divided into 3 groups’ | Healthy primiparous women (Low risk of pre-eclampsia) | 120 mg calcium daily versus 240 mg calcium daily (combined in this analysis) versus no calcium | High |
| Herrera (1998)22 | Allocated to active tablets or identical-looking placebo by means of sequentially numbered, sealed allocation cards in computer-generated random sequence. | Primigravidas with risk factors for pre-eclampsia, positive roll-over test and high mean blood pressure; low dietary calcium (High risk of pre-eclampsia). Setting: Colombia, black and mixed race women, socio-economic levels 1 and 2. | 450 mg linoleic acid plus 600 mg calcium versus placebo in the third trimester | Low |
| Herrera (2006)23 | Allocated to active tablets or identical-looking placebo by means of sequentially numbered, sealed allocation cards in computer-generated random sequence. | Primigravidas <19 years or >35 years old, with risk factors for pre-eclampsia, abnormal uterine artery Doppler ultrasound, low dietary calcium (High risk of pre-eclampsia). Setting: Bangladesh and Colombia. Median daily dietary calcium 602 in the calcium group and 576 in the placebo group. | 450 mg conjugated linoleic acid plus 600 mg calcium versus placebo from 18 to 22 weeks until delivery | Low |
| Marya (1987)19 | ‘Randomly selected’ | Pregnant women 20–35 years old, low dietary calcium (Low risk of pre-eclampsia) | Calcium 375 mg plus Vit D 1200 IU from 20 to 24 weeks of pregnancy onwards versus control | High |
| Rogers (1999)18 | Randomised in ratio 1:2:2 using five unsealed envelopes, selected by participants | Primiparous women in second trimester with rested left lateral automated blood pressureBP MAP 60 mmHg or more (Low risk of pre-eclampsia) | Calcium 600 mg daily from 22 to 32 weeks, then 1200 mg daily versus controls | High |
| Rumiris (2006)21 | Double-blind, placebo-controlled trial. Randomised according to a computer-generated random number sequence by an independent third party. | Pregnant women with low antioxidant status at 8–12 weeks of gestation. No medical complications or current use of trial supplements. (High risk of pre-eclampsia). Setting, antenatal clinic, University of Indonesia. | Calcium 800 mg, N-acetylcysteine 200 mg, copper 2 mg, zinc 15 mg, manganese 0.5 mg, and selenium 100 μg and vitamins A 1000 IU, B6 2.2 mg, B12 2.2 μg, C 200 mg and E 400 IU, from 8 to 12 weeks of gestation throughout pregnancy. | Low |
| Taherian (2002)20 | ‘randomised and divided into 3 groups’ | Healthy nulliparous women (Low risk of pre-eclampsia) | 500 mg calcium + 200 IU vitamin D from 20th week of pregnancy till delivery versus control | High |