Imdad et al. BMC Public Health 2011, 11(Suppl 3):S18 http://www.biomedcentral.com/1471-2458/11/S3/S18 Page 8 of 13 Study or Subgroup Belizan 1991 Kumar 2009 L-Jaramillo 1990 Purwar 1996 Villar 2006 Total (95% CI) Total events 452 515 Heterogeneity: Chi² = 6.21, df = 4 (P = 0.18); I² = 36% Test for overall effect: Z = 2.13 (P = 0.03) Calcium Placebo Risk Ratio Events Total Events Total Weight M-H, Fixed, 95% CI Risk Ratio M-H, Fixed, 95% CI 33 527 19 273 0 22 2 97 398 4038 4957 37 542 7.1% 32 251 6.5% 4 34 0.7% 6 93 1.2% 436 4042 84.6% 0.92 [0.58, 1.44] 0.55 [0.32, 0.94] 0.17 [0.01, 2.99] 0.32 [0.07, 1.54] 0.91 [0.80, 1.04] 4962 100.0% 0.88 [0.78, 0.99] 0.01 0.1 1 10 100 Favours experimental Favours control Figure 5 Effect of calcium supplementation during pregnancy on risk of preterm birth in developing countries. number of events being less than 50 (Rule 1) [12]. Therefore, severe morbidity outcomes were considered. Considering the direction of effect, value of effect size and statistical significance of the estimates, reduction in severe maternal morbidity/mortality was chosen for inclusion in the LiST (Rule 3).This combined outcome was reported by one study and included severe gesta- tional hypertensive related morbidities that can lead to maternal mortality [44]. The qualitative assessment of this estimate was that of ‘moderate’ level however down- graded to ‘low’ to translate it to maternal mortality[47]. To estimate the effectiveness of calcium supplementa- tion during pregnancy on neonatal outcomes, CHERG rules were applied to the outcomes of neonatal mortal- ity, preterm birth, and small for gestational age and low birth weight. One study reported all-cause neonatal mortality which showed significant reduction of 30 % with 37 events in the intervention and 53 events in con- trol group [44]. The overall quality grade for this esti- mate was that of moderate level which was also downgraded to ‘low’ for translating all-cause into cause specific mortality. This estimate for reduction in all- Study or Subgroup Belizan 1991 Kumar 2009 Villar 2006 Total (95% CI) Total events 562 597 Heterogeneity: Tau² = 0.05; Chi² = 5.09, df = 2 (P = 0.08); I² = 61% Test for overall effect: Z = 1.27 (P = 0.20) Calcium Placebo Risk Ratio Events Total Events Total Weight M-H, Random, 95% CI Risk Ratio M-H, Random, 95% CI 31 547 19 273 512 3930 4750 41 559 26.9% 32 251 22.1% 524 3938 51.0% 0.77 [0.49, 1.21] 0.55 [0.32, 0.94] 0.98 [0.87, 1.10] 4748 100.0% 0.81 [0.58, 1.12] 0.01 0.1 1 10 100 Favours experimental Favours control Figure 6 Effect of calcium supplementation during pregnancy on risk of Low Birth Weight (< 2500 g).