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Evidence-Based Supplement Research
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Calcium and Reduced Stillbirth

Research synthesisLow evidenceSmall effect3 studies · 1 beneficial · 2 neutral · 0 harmful

Across 3 studies (all meta-analyses of RCTs), 2 reported neutral small effects and 1 reported a beneficial small effect of calcium supplementation on stillbirth, but none reached statistical significance. The predominant effect size is small, and most evidence is in pregnant women, with calcium carbonate used in one study. The evidence base is very small and does not support a clear benefit.

  • Effective dose range: 1000 mg/day or greater (calcium carbonate in one study)
  • Studied populations: pregnant women (including those with prior pre-eclampsia/eclampsia)

Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. Many of the included studies did not reach statistical significance — effect may be smaller than the predominant direction suggests. Effect estimates have wide confidence intervals crossing 1.0, and certainty of evidence ranged from very low to moderate.

Generated Jul 12, 2026
Doses used in studies
  • Calcium Carbonate · mg/day: 1,000 (median 1,000, IQR 1,000–1,000) — 1 study
  • mg/day: 1,000 (median 1,000, IQR 1,000–1,000) — 1 study
Safety in these studies
  • Overall tolerabilityNo significant differenceSerious adverse eventRR 0.97, 95% CI 0.70 to 1.35

    The evidence is very uncertain about the effect of calcium, compared to placebo, on maternal death or severe morbidity (RR 0.97, 95% CI 0.70 to 1.35; 1 RCT, 1355 women; RD 3/1000 fewer, 95% CI 29 fewer to 34 more; very low-certainty evidence).

    from: Calcium supplementation commenced before pregnancy for preventing hypertensive disorders a
  • gall stonesNo significant difference

    There was no evidence that calcium supplementation had any effect on maternal weight gain during pregnancy; increasing bone mineral density in pregnant women; rate of intrauterine growth restriction; perinatal mortality; stillbirth or fetal death rate; increase birth length or fetal head circumference; and adverse effects such as postpartum haemorrhage, gall stones, gastrointestinal symptoms, headache, urinary stones, urinary tract infection or impaired renal function.

    from: Calcium supplementation (other than for preventing or treating hypertension) for improving
  • gastrointestinal symptomsNo significant difference

    There was no evidence that calcium supplementation had any effect on maternal weight gain during pregnancy; increasing bone mineral density in pregnant women; rate of intrauterine growth restriction; perinatal mortality; stillbirth or fetal death rate; increase birth length or fetal head circumference; and adverse effects such as postpartum haemorrhage, gall stones, gastrointestinal symptoms, headache, urinary stones, urinary tract infection or impaired renal function.

    from: Calcium supplementation (other than for preventing or treating hypertension) for improving
  • headacheNo significant difference

    There was no evidence that calcium supplementation had any effect on maternal weight gain during pregnancy; increasing bone mineral density in pregnant women; rate of intrauterine growth restriction; perinatal mortality; stillbirth or fetal death rate; increase birth length or fetal head circumference; and adverse effects such as postpartum haemorrhage, gall stones, gastrointestinal symptoms, headache, urinary stones, urinary tract infection or impaired renal function.

    from: Calcium supplementation (other than for preventing or treating hypertension) for improving
  • impaired renal functionNo significant difference

    There was no evidence that calcium supplementation had any effect on maternal weight gain during pregnancy; increasing bone mineral density in pregnant women; rate of intrauterine growth restriction; perinatal mortality; stillbirth or fetal death rate; increase birth length or fetal head circumference; and adverse effects such as postpartum haemorrhage, gall stones, gastrointestinal symptoms, headache, urinary stones, urinary tract infection or impaired renal function.

    from: Calcium supplementation (other than for preventing or treating hypertension) for improving
  • low birthweightNo significant differenceaverage RR 0.93, 95% CI 0.81 to 1.07

    and may have little or no effect on low birthweight (less than 2500 g) (average RR 0.93, 95% CI 0.81 to 1.07; 6 trials, 14,162 women; low-certainty evidence)

    from: Calcium supplementation (other than for preventing or treating hypertension) for improving
  • postpartum haemorrhageNo significant difference

    There was no evidence that calcium supplementation had any effect on ... adverse effects such as postpartum haemorrhage, gall stones, gastrointestinal symptoms, headache, urinary stones, urinary tract infection or impaired renal function.

    from: Calcium supplementation (other than for preventing or treating hypertension) for improving
  • postpartum hemorrhageNo significant difference

    There was no evidence that calcium supplementation had any effect on maternal weight gain during pregnancy; increasing bone mineral density in pregnant women; rate of intrauterine growth restriction; perinatal mortality; stillbirth or fetal death rate; increase birth length or fetal head circumference; and adverse effects such as postpartum haemorrhage, gall stones, gastrointestinal symptoms, headache, urinary stones, urinary tract infection or impaired renal function.

    from: Calcium supplementation (other than for preventing or treating hypertension) for improving
  • preterm birth less than 34 weeksNo significant differenceaverage RR 1.03, 95% CI 0.79 to 1.35

    but probably has little effect on the risk of preterm birth less than 34 weeks (average RR 1.03, 95% CI 0.79 to 1.35; 3 trials, 5569 women; moderate-certainty evidence)

    from: Calcium supplementation (other than for preventing or treating hypertension) for improving
  • preterm birth less than 37 weeksNo significant differenceaverage RR 0.80, 95% CI 0.65 to 0.99

    Calcium supplementation probably slightly reduces the risk of preterm birth less than 37 weeks (average risk ratio (RR) 0.80, 95% confidence interval (CI) 0.65 to 0.99; 11 trials, 15,379 women; moderate-certainty evidence)

    from: Calcium supplementation (other than for preventing or treating hypertension) for improving
  • urinary stonesNo significant difference

    There was no evidence that calcium supplementation had any effect on maternal weight gain during pregnancy; increasing bone mineral density in pregnant women; rate of intrauterine growth restriction; perinatal mortality; stillbirth or fetal death rate; increase birth length or fetal head circumference; and adverse effects such as postpartum haemorrhage, gall stones, gastrointestinal symptoms, headache, urinary stones, urinary tract infection or impaired renal function.

    from: Calcium supplementation (other than for preventing or treating hypertension) for improving
  • urinary tract infectionNo significant difference

    There was no evidence that calcium supplementation had any effect on maternal weight gain during pregnancy; increasing bone mineral density in pregnant women; rate of intrauterine growth restriction; perinatal mortality; stillbirth or fetal death rate; increase birth length or fetal head circumference; and adverse effects such as postpartum haemorrhage, gall stones, gastrointestinal symptoms, headache, urinary stones, urinary tract infection or impaired renal function.

    from: Calcium supplementation (other than for preventing or treating hypertension) for improving
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