TL;DR

• Calcium has long been included in prenatal supplements partly on the belief that it helps prevent pre-eclampsia, a serious pregnancy complication.
• A major 2025 update to the Cochrane review on this topic, led by researchers at Stellenbosch University, found high-certainty evidence from large, reliable trials that calcium supplementation did not reduce pre-eclampsia risk. Excluding studies that failed updated eligibility or trustworthiness assessments substantially changed the earlier picture.
• WHO currently still recommends 1.5 to 2.0 g of elemental calcium a day in pregnant women with low dietary calcium intake, specifically to reduce pre-eclampsia risk. That guidance predates this Cochrane update, so whether it changes in response remains to be seen.
• Calcium still matters in pregnancy for bone health and general maternal and fetal needs, that part of the story hasn't changed.
• We use dicalcium malate, a directly studied, bioavailable calcium source, though the evidence doesn't support calling it definitively superior to other well-absorbed calcium forms.
• Most prenatal supplements, including ours, provide a modest calcium dose by design, on the assumption that food, including dairy and other calcium-rich sources, covers a meaningful share of daily needs.

Why calcium has been in prenatals

Calcium is essential for building and maintaining bone, for muscle and nerve function, and for a developing baby's own skeleton. Beyond that general role, calcium supplementation has specifically been recommended in pregnancy for another reason: a belief that it helps prevent pre-eclampsia, a serious condition involving high blood pressure and organ stress that can be life-threatening for both mother and baby.

New evidence complicates that second reason

In late 2025, researchers at Stellenbosch University published a major update to the Cochrane review on calcium supplementation and pre-eclampsia, pooling 10 randomised controlled trials and over 37,500 participants. The finding was blunt: high-certainty evidence from the large, reliable trials that calcium supplementation did not reduce pre-eclampsia risk. The review also did not identify clear benefits for outcomes such as maternal death, preterm birth or neonatal mortality, although these outcomes were less common and the certainty of evidence was lower than for pre-eclampsia.

What changed wasn't the biology, it was the quality of evidence being counted. Earlier reviews had included a number of older studies that were excluded from this update for several reasons, including changed eligibility criteria, trustworthiness concerns identified through newer methods for detecting unreliable trial data, and other methodological problems. Once those studies were excluded, the apparent protective effect against pre-eclampsia disappeared. As the review's co-author put it, once you account for small-trial effects and publication bias, "the evidence supporting calcium supplementation to prevent pre-eclampsia simply doesn't hold up." You can read the full write-up from Stellenbosch University here: New evidence questions the benefit of calcium supplements in pregnancy for preventing pre-eclampsia.

This is a live discrepancy between evidence and guidance worth knowing about. WHO currently still recommends 1.5 to 2.0 g of elemental calcium a day during pregnancy in populations with low dietary calcium intake, specifically to reduce pre-eclampsia risk, and NIH's current guidance similarly still says supplementation "may reduce" pre-eclampsia risk among women with insufficient calcium intake, while acknowledging weaknesses in much of the underlying evidence. Both of those positions predate this Cochrane update. Whether either changes in response remains to be seen, but it isn't a settled question we can call either way for you.

Worth being clear about what this doesn't mean: it isn't evidence that calcium is harmful or unnecessary in pregnancy, only that the specific claim of pre-eclampsia prevention was built on a shakier evidence base than assumed.

Why calcium still belongs in the conversation

Calcium's role in maternal bone health and fetal skeletal development doesn't depend on the pre-eclampsia question. Pregnancy places real demands on maternal calcium stores as the baby's skeleton develops, and dietary intake in many women, including a meaningful share of pregnant women in well-resourced countries, still falls short of recommended levels, about one in five pregnant women in the US has calcium intake below the estimated average requirement. That's a separate, more basic reason calcium remains a sensible part of prenatal nutrition, even with the pre-eclampsia-specific claim now on much weaker footing.

Not all calcium forms are the same

Calcium supplements come in several forms, including carbonate, citrate and malate-based salts. The accompanying compound can affect characteristics such as elemental calcium content, solubility, and how the supplement behaves during digestion.

We use dicalcium malate. It's worth being direct about what the evidence for this exact form does and doesn't show. In a small crossover study in healthy adults comparing dicalcium malate with calcium carbonate and two calcium amino-acid chelates, each providing 900 mg of elemental calcium, overall calcium exposure was similar across all four formulations. Dicalcium malate showed the longest serum half-life of the group, while calcium carbonate reached its peak concentration fastest and was itself absorbed efficiently. The European Food Safety Authority separately assessed dicalcium malate and concluded that calcium is bioavailable from the ingredient, but that its bioavailability appears similar to other calcium sources already permitted for use, rather than superior. EFSA also noted the ingredient doesn't fully dissociate under simulated digestive conditions, and that the available evidence didn't establish a clear difference between dicalcium malate and standard calcium malate, already an approved calcium source.

So our reasoning for using dicalcium malate isn't a claim that it's been proven more bioavailable than carbonate or other well-absorbed forms, the evidence doesn't support that. It's a directly studied, legitimate calcium source with formulation characteristics that suited a daily multi-nutrient product. Calcium carbonate is known to cause more gastrointestinal side effects, gas, bloating and constipation, than some other calcium forms, particularly in people with lower stomach acid, but that comparison is best established for calcium citrate specifically. We don't have strong head-to-head evidence showing that dicalcium malate itself causes fewer gastrointestinal effects than carbonate, so we don't claim a proven tolerability advantage.

Why the dose is lower than the full daily requirement

The recommended calcium intake in pregnancy is 1,000 mg a day for most adult women. Most prenatal supplements, including ours, provide meaningfully less than that, and that's common across the category rather than unusual: in a US analysis of 188 prenatal supplements, 78% contained calcium, but the median amount was only 200 mg per serving. That's a deliberate design choice rather than an oversight. It assumes that a meaningful share of daily calcium comes from food, including dairy products, fortified alternatives like calcium-set tofu or fortified plant milks, and calcium-rich vegetables, rather than needing to be delivered entirely through a supplement.

To put that in perspective: a glass of milk provides roughly 300 mg of calcium, a serving of yoghurt provides around 200 mg or more, and a slice of cheddar cheese provides around 120 mg. Combining a couple of calcium-rich foods across a day covers a substantial share of the daily target without any supplement involved at all.

There's also a practical timing consideration. WHO recommends taking calcium and iron supplements several hours apart because concomitant dosing may interfere with iron absorption. Keeping the supplemental calcium dose modest, rather than pushing a single tablet toward the full 1,000 mg, also helps keep the product a manageable size for something meant to be taken daily for months.

If your diet includes little dairy or other calcium-rich food, it's worth discussing your individual calcium intake with a doctor or dietitian rather than assuming a standard prenatal dose covers the gap.

This article is for general educational purposes and isn't medical advice. Please consult a doctor or dietitian about your individual calcium needs, particularly if you have limited dairy or calcium-rich food intake, a history of pre-eclampsia, or are taking other medication or supplements that may interact with calcium.

Sources

1. Rohwer AC, Cluver C, et al. Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems. Cochrane Database of Systematic Reviews, 2025. https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD001059.pub6/full

2. New evidence questions the benefit of calcium supplements in pregnancy for preventing pre-eclampsia. Stellenbosch University Faculty of Medicine and Health Sciences, 4 December 2025. https://www.su.ac.za/en/faculties/medicine/news/new-evidence-questions-benefit-calcium-supplements-pregnancy-preventing-pre-eclampsia

3. National Institutes of Health, Office of Dietary Supplements. Dietary Supplements and Life Stages: Pregnancy, Health Professional Fact Sheet. https://ods.od.nih.gov/factsheets/Pregnancy-HealthProfessional/

4. National Institutes of Health, Office of Dietary Supplements. Calcium: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/

5. World Health Organization. Calcium supplementation in pregnant women. https://www.who.int/tools/elena/interventions/calcium-pregnancy

6. Chaturvedi P, Mukherjee R, McCorquodale M, Crawley D, Ashmead S, Guthrie N. Comparison of calcium absorption from various calcium-containing products in healthy human adults: a bioavailability study. The FASEB Journal, 2006;20(5):A1063-A1064. doi:10.1096/fasebj.20.5.A1063-c

7. EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS). Evaluation of di-calcium malate, used as a novel food ingredient and as a source of calcium in foods for the general population, food supplements, total diet replacement for weight control and food for special medical purposes. EFSA Journal, 2018;16(6):5291. https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2018.5291