Calcium, Magnesium, & Zinc Supplement Safety During Pregnancy

Pregnancy increases your need for various vitamins and minerals so your baby can grow and develop properly. Calcium, magnesium and zinc are just a few of the nutrients you need.

Your health-care provider will most likely prescribe a prenatal vitamin to ensure that you get adequate amounts of the nutrients you need during pregnancy. Taking additional supplements may be harmful. Check with your health-care provider before taking any supplements.

Recommended Dietary Allowances

The recommended dietary allowance, or RDA, for calcium during pregnancy is 1,000 mg per day, with an upper limit of 2,500.

The RDA for magnesium is 360 mg per day, with an upper limit of 350 mg per day from supplements, and the RDA for zinc during pregnancy is 11 mg per day, with an upper limit of 40 mg per day. Taking more than the upper limit of these minerals may have a harmful effect on you and your baby.


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According to the University of Maryland Medical Center, magnesium regulates the amount of calcium and zinc in the body. Magnesium is also the preferred treatment to prevent or treat seizures as a result of eclampsia, which may occur in the third trimester of pregnancy. It is given through an IV in the hospital. Calcium is needed for strong bones and teeth.

Most pregnant women don’t get enough calcium in their diet so supplementation may be needed.

The Linus Pauling Institute at Oregon State University states that zinc is necessary for growth and development, the immune response and neurological function. A prenatal vitamin should provide adequate amounts of calcium, magnesium and zinc during your pregnancy.

Expert Insight

J. T. Repke from the department of gynecology and obstetrics at Johns Hopkins University published a study in the June 1991 issue of the journal “Clinical Obstetrics and Gynecology” regarding calcium, magnesium and zinc supplementation and perinatal outcome.

Repke found that the evidence is weak for magnesium supplementation and improving perinatal outcome. The routine use of zinc supplementation cannot be recommended at this time, but calcium supplementation is required for about two-thirds of pregnant women due to lack of calcium in the diet.

Prenatal Supplements

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The American Pregnancy Association recommends taking one prenatal multivitamin as prescribed by your doctor. When you take various vitamins and supplements, you run the risk of overdosing on a certain vitamin or mineral, which may cause harm to you or your baby.


Magnesium can interfere with other medications and competes with calcium for absorption.

If your calcium levels are already low, taking more magnesium may result in even lower levels of calcium.

Zinc toxicity can result in abdominal pain, diarrhea, nausea and vomiting. Consult with your health-care provider before taking any supplements during your pregnancy.