science

Magnesium and Pregnancy: What You Need to Know

Dr. Carla Montrond Correia ND, CNS

Medically reviewed by

Dr. Carla Montrond Correia ND, CNS

5 min read

woman holding her pregnant belly

Magnesium is a very important mineral, and that is especially so during pregnancy. Read more to learn why and to see if a supplement is right for you.

What is magnesium?

Magnesium is an important mineral in your body and is found in more than 300 of your body’s enzyme systems. These systems help regulate and maintain important biochemical processes in your body, including blood pressure regulation, muscle and nerve function, and blood glucose control. Maintaining healthy magnesium levels is essential to your body’s health – especially, as it turns out, during pregnancy. Magnesium is found naturally in many foods, is added to other foods, and is available in supplement form.

Why do pregnant women need to take magnesium?

During pregnancy, it’s important to maintain your health, both for yourself and for the fetus. When you’re pregnant, it is hypothesized that your body ends up using more magnesium due to the changes happening in the body, that’s why it’s important to maintain healthy magnesium levels.

For those who don’t have adequate levels of magnesium, taking magnesium can be a good idea. A study from the National Institutes of Health found that many pregnant people, especially those from disadvantaged backgrounds, have magnesium intakes lower than the recommended levels. In the same study, it was shown that women who took a magnesium supplement during pregnancy had healthier pregnancies than those in the placebo group.

For pregnant people, magnesium has also been shown to help prevent high blood pressure brought on by pregnancy, which in turn can help prevent other pregnancy complications. It’s also been shown to help maintain healthy bones, healthy muscle function, healthy blood sugar levels, and healthy blood pressure, while also supporting a healthy uterus and healthy fetal growth.

Pregnancy benefits from magnesium

As mentioned above, magnesium has been shown to help pregnant people maintain healthy bones, healthy muscle function, healthy blood sugar levels, and healthy blood pressure. But that’s not all magnesium can do. Indeed, studies point to the significant benefits of magnesium both for fetal health and maternal health – before and after the child is born.

One study of 568 women examined the effect of magnesium supplementation in pregnancy. The women were divided into two groups: One received magnesium-aspartate-hydrochloride (a common magnesium supplement) per day for 16 weeks, while the other group received a tablet of aspartic acid as a placebo. Allocation to the two groups was determined based on when the women were due to give birth. The findings were stark: The study found that magnesium supplementation during pregnancy was associated with fewer maternal hospitalizations and a reduced likelihood of preterm labor. (Preterm labor is often due to uterine hyperexcitability caused by a chronic magnesium deficiency.)

The benefits extended beyond the point of birth, too, with the newborns from the magnesium group being less likely to be referred to the neonatal intensive care unit.

That’s not all. A review of ten randomized studies – involving more than 9,000 women – found that magnesium supplementation during pregnancy may help address blood sugar issues related to pregnancy. Magnesium infusion is in fact a standard therapeutic measure for people who develop blood pressure issues during pregnancy. The same review also found that magnesium could increase the newborn’s birth weight. It’s important to note, however, that this study found that current evidence isn’t sufficient to make recommendations for the use of magnesium supplementation during pregnancy. There’s a real need for larger, well-designed randomized trials to gather more evidence. The main goal is to increase magnesium intake through food sources and use supplements to bridge any nutrient gaps.

One more thing: When we’re talking about pregnancy’s effects on the body, we can’t forget about those annoying leg cramps. Leg cramps are quite common for pregnant people. Fortunately, a recent study showed that magnesium supplements can decrease leg cramps and their related discomfort. Per this study, if these kinds of leg cramps are a problem for you, a magnesium supplement can be a “valuable therapeutic tool".

Symptoms of being deficient in magnesium

Some symptoms of magnesium deficiency include:

  • loss of appetite
  • nausea and vomiting
  • sleepiness
  • fatigue and weakness
  • shaking
  • pins and needles
  • muscle spasms
  • hyperexcitability

If you notice any of these symptoms, it is best to seek medical attention right away.

Dosing recommendations for pregnant women

The recommended daily allowance (RDA) of magnesium for pregnant people is 350-400 mg, compared with 300-310 mg for non-pregnant and non-lactating people. The increase is due to the needs of the fetus and the imperative of balancing the changes happening in the body. During lactation, the RDA is 310-360 mg per day.

How to know when you’re getting too much magnesium

You really don’t need to worry about getting too much magnesium from food sources. However, it is possible to get too much in supplement form. If you’re experiencing any of the following symptoms, you may be getting too much magnesium, and should discuss with a medical professional:

  • Nausea
  • Diarrhea
  • Muscle weakness
  • Fatigue

Do you need a standalone magnesium supplement or is a prenatal enough?

The question of whether you need a standalone magnesium supplement if you’re already taking a prenatal vitamin is a good one. The answer is: It depends on how much magnesium is present in your prenatal. If it’s already supplying you with around 400 mg of magnesium per day, then you probably want to avoid a specific supplement – getting too much magnesium in supplement form can have negative side effects. Instead of doubling up on supplements, you can incorporate more magnesium-rich foods into your diet.

Is it safe to take magnesium while pregnant?

It is safe to take magnesium while pregnant. The key is to make sure you’re not exceeding the RDA for pregnant people (depending on age), which is 350-400 mg. If you’re taking a prenatal vitamin that includes magnesium, you may want to avoid taking an additional magnesium supplement. Talk to your doctor about your body’s particular needs and what’s right for you.

Best foods with magnesium during pregnancy

There are fortunately many tasty magnesium-rich foods out there that you can enjoy during pregnancy. Some of these foods include: nuts, unrefined grains and grain products, fish, seafood, vegetables, legumes, berries, and leafy greens. Even getting more tap or bottled water can make a contribution to your magnesium intake.

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