Imdad et al. BMC Public Health 2011, 11(Suppl 3):S18 http://www.biomedcentral.com/1471-2458/11/S3/S18 Page 7 of 13 Calcium Placebo Risk Ratio Study or Subgroup Events Total Events Total Weight M-H, Random, 95% CI 2.4.1 Low risk women Belizan 1991 57 579 87 588 22.9% 0.67 [0.49, 0.91] Purwar 1996 8 97 27 93 14.8% 0.28 [0.14, 0.59] Villar 2006 613 4151 645 4161 25.7% 0.95 [0.86, 1.05] Subtotal (95% CI) 4827 4842 63.4% 0.64 [0.39, 1.05] Total events 678 759 Heterogeneity: Tau² = 0.15; Chi² = 14.21, df = 2 (P = 0.0008); I² = 86% Test for overall effect: Z = 1.77 (P = 0.08) Risk Ratio M-H, Random, 95% CI 2.4.2 High risk women L-Jaramillo 1990 2 55 12 51 6.6% L-Jaramillo 1997 3 22 24 34 10.0% Niromonesh 2001 10 15 11 15 19.9% Subtotal (95% CI) 92 100 36.6% Total events 15 47 Heterogeneity: Tau² = 1.76; Chi² = 16.97, df = 2 (P = 0.0002); I² = 88% Test for overall effect: Z = 1.37 (P = 0.17) Total (95% CI) 4919 4942 100.0% Total events 693 806 Heterogeneity: Tau² = 0.19; Chi² = 27.84, df = 5 (P < 0.0001); I² = 82% Test for overall effect: Z = 2.72 (P = 0.007) 0.15 [0.04, 0.66] 0.19 [0.07, 0.57] 0.91 [0.57, 1.45] 0.32 [0.06, 1.63] 0.55 [0.36, 0.85] 0.01 0.1 1 10 100 Favours experimental Favours control Figure 4 Effect of calcium supplementation during pregnancy on risk of development of gestational hypertension (±proteinuria) in developing countries. during pregnancy seems to have a more prominent pre- ventive effect of calcium supplementation [RR 0.32, 95 % CI 0.06-1.63] compared to those at lower risk [RR 0.64, 95 % CI 0.39-1.05], however the results were not statistically significant for both the subgroups (Figure 4). Neonatal outcomes One study reported effect of calcium supplementation during pregnancy on neonatal mortality [44]. There was a significant reduction of 30 % in the intervention group compared to placebo (RR 0.70; 95 % CI 0.56-0.88). Data on preterm births were included from five trials [37,38,40,43,44] and the pooled analysis showed a signifi- cant reduction of 12% (RR 0.88; 95% CI 0.78-0.99) in the intervention group compared to control (Figure 5). The overall grade for this estimate was that of ‘high level’. The outcome of risk of low birth weight in newborn was reported in three trials [37,38,44] showing no impact of calcium supplementation compared to control (RR 0.81 95% CI 0.58-1.12) (Figure 6). Combined data from two studies [43,44] showed a non-significant reduction in risk of small for gestational babies (RR 0.90; 95 % 0.59-1.38) (data not shown). The overall quality grade for both of the above estimates was that of ‘moderate’ level. Recommendations for LiST We followed standardized guidelines of Child Health Epidemiology Reference Group (CHERG) to get a point estimate for effectiveness of calcium supplementation during pregnancy in reducing maternal and neonatal mortality related to gestational hypertensive disorders in developing countries [12]. These rules were applied to collective mortality and morbidity outcomes to get a most appropriate estimate for inclusion in the LiST model. The final decision about the best estimate is based on three components 1) the volume and consis- tency of the evidence 2) the size of risk ratio and 3) the strength of the statistical evidence for an association between the intervention and outcome, as reflected by the p-value [12]. More details about application of CHERG rules are provided in the methods paper [12]. Additional File 1 details the quality assessment of the calcium supplementation trials on maternal and neona- tal outcomes. Table 2 presents the application of CHERG rules applied to collective maternal mortality and morbidity outcomes. The data on maternal mortal- ity was reported in only one study [44], with a total of 7 events in both arms, which could not be used due to