Magnesium During Pregnancy: Why You Should Take It And How Much

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Your need for magnesium increases when you are pregnant. The essential mineral performs different functions during pregnancy.

It is required to maintain healthy blood sugar levels in the body (1). It helps build healthy teeth and bones and works in partnership with calcium. It also regulates cholesterol and irregular heartbeat (2). Physical and emotional stress also increases the need for magnesium.

A severe deficiency of magnesium during pregnancy can lead to preeclampsia (high blood pressure and seizures), preterm labor, infant mortality, and congenital disabilities (3).

MomJunction tells you why magnesium is such a vital element, what effect it has on the baby, and much more.

[ Read: Calcium Rich Foods You Should Eat During Pregnancy ]

Why Is Magnesium Important During Pregnancy?

Other than the primary reasons mentioned above, there are more ways in which magnesium works for you and your baby.

  1. Works in conjunction with calcium: Both these minerals work together. While magnesium induces relaxation to the muscles, calcium stimulates muscle contractions. The right levels of magnesium can also keep the uterus from contracting until 35 weeks of pregnancy.
  1. Lowers the risk of osteoporosis: Adequate levels of magnesium and calcium may help reduce the chance of bone damage later in life (4).
  1. Reduces cramps: Cramping is very common during pregnancy. Magnesium reduces cramps, lessens the strength of Braxton Hicks contractions, and also treats constipation (5).
  1. Acts as a tranquilizer: Magnesium is the best remedy for busting stress and insomnia, which are quite common during pregnancy. Doctors usually prescribe it as a separate supplement apart from the prenatal vitamin/mineral supplements.
  1. Helps in delivery: This mineral optimizes blood pressure levels and improves the pain tolerance threshold, possibly making your delivery more comfortable.
  1. Curbs nausea: Magnesium can treat nausea, which is the most common sickness along with morning sickness.
  1. Treats headaches: Magnesium supplementation may lessen the incidence of migraine headaches during pregnancy. It helps in relaxing constricted blood vessels in the brain, preventing lactic acid buildup, which may otherwise cause tension and migraine pain (6).
  1. Lowers risk of cerebral palsy: According to a review published in Australia, magnesium sulfate when given to mothers who are at risk of preterm labor helped in protecting their babies from cerebral palsy (7).

[ Read: Swelling During Pregnancy ]

Effects Of Magnesium On The Baby

Research studies have revealed that intake of magnesium during pregnancy will either show a positive benefit or no benefit to the baby.

  • Magnesium supplementation shows a beneficial effect on the growth of the fetus (8).
  • Oral magnesium supplementation improves fetal circulation (9).
  • Newborns who had better sleep and wake cycles came from mothers who had taken sufficient magnesium during pregnancy.

How Much Magnesium Do You Need During Pregnancy?

The recommended daily allowance of magnesium during pregnancy is 350 to 360 milligrams. If you are between 19 and 30 years, you require 350mg, and if you are 31 years and above, you need 360mg (10). Vomiting, nausea, and food aversions during pregnancy may make you deficient in magnesium. Therefore, supplementation may be necessary apart from including magnesium-rich foods in your diet.

[ Read: Vomiting During Pregnancy ]

Magnesium-Rich Foods For Pregnant Women

To supplement your body with the recommended magnesium dosage, you should eat a healthy diet. Many plant and animal sources rich in magnesium include leafy greens (spinach), whole grains, seeds, legumes, breakfast cereals, foods containing dietary fiber, and fortified foods. Processed foods are a less optimal choice. Also, the magnesium in water alters from 1mg to 120mg per liter.

The following table gives you an idea of what foods can be included as a part of magnesium-rich diet.

Almonds, dry roasted, 1 ounceSERVING20
Spinach, boiled, ½ cup7820
Cashews, dry roasted, 1 ounce7419
Peanuts, oil roasted, ¼ cup6316
Cereal, shredded wheat, 2 large biscuits6115
Soymilk, plain or vanilla, 1 cup6115
Black beans, cooked, ½ cup6015
Edamame, shelled, cooked, ½ cup5013
Peanut butter, smooth, 2 tablespoons4912
Bread, whole wheat, 2 slices4612
Avocado, cubed, 1 cup4411
Potato, baked with skin, 3.5 ounces4311
Rice, brown, cooked, ½ cup4211
Yogurt, plain, low fat, 8 ounces4211
Breakfast cereals, fortified with 10% of the DV for magnesium4010
Oatmeal, instant, 1 packet369
Kidney beans, canned, ½ cup359
Banana, 1 medium328
Salmon, Atlantic, farmed, cooked, 3 ounces267
Milk, 1 cup24–276–7
Halibut, cooked, 3 ounces246
Raisins, ½ cup236
Chicken breast, roasted, 3 ounces226
Beef, ground, 90% lean, pan broiled, 3 ounces205
Broccoli, chopped and cooked, ½ cup123
Rice, white, cooked, ½ cup103
Apple, 1 medium92
Carrot, raw, 1 medium72


Weave your menu plan around these food items to make sure you are getting enough magnesium for you and your baby!

Do You Need Magnesium Supplements?

It is very tempting to just pop in a few supplements instead of watching what we eat. But is magnesium supplement a good idea?

Anything in excess can harm your body. You should take magnesium supplements only if your diet isn’t giving you enough magnesium. But never self-medicate. Always consult your doctor and take the supplements only if they recommend. In fact, many doctors prescribe them as a part of the prenatal vitamin package.

[ Read: Prevent Leg Cramps During Pregnancy ]

Are There Any Side Effects To Magnesium Supplements?

The chance of consuming too much magnesium through food is slim. But when you use supplements, you run the risk of magnesium overdose. Here are some side effects that may come with too much magnesium through supplements.

1. Diarrhea and dehydration

Magnesium supplements can cause intestinal irritation in some pregnant women. This can lead to diarrhea, abdominal cramping, and appetite loss. Untreated diarrhea can even lead to dehydration – a serious concern during pregnancy. If you are on magnesium supplements and are experiencing diarrhea for two to three days, talk to your doctor.

[ Read: Diarrhea During Pregnancy ]

2. Stomach upset

The last thing you need during pregnancy is nausea and vomiting – morning sickness provides enough of that! But magnesium intake can lead to digestive issues that mimic morning sickness. These symptoms subside within hours of treatment but if they persist, seek medical advice.

3. Medication interactions

Magnesium supplements are known to interact with certain medications. If you are on antibiotics, blood pressure medication, calcium channel blockers, diabetes medication, etc., talk to your doctor before you start the supplements. Always review all medications and supplements you are taking during pregnancy, with your doctor.

4. Overdose:

If you experience any of the following symptoms after consuming magnesium supplements, head to the ER. Magnesium overdose can be fatal if not treated on time.

Symptoms to look out for:

  • Persistent vomiting
  • Irregular heart rate
  • Difficulty breathing
  • Muscle weakness
  • Low blood pressure
  • Confusion

During pregnancy, your body needs that little extra care and nourishment. But you don’t always need to grab OTC medication and supplements to meet these needs. Try your best to eat healthy and keep in touch with your doctor. Moving further, let’s understand magnesium salts, and how they are useful in pregnancy.

[ Read: Iron During Pregnancy ]

Magnesium Sulfate During Pregnancy

Magnesium sulfate, a magnesium salt, is prescribed to prevent premature birth and decrease uterine tone.

What are its functions?

Magnesium sulfate is available in two forms – white powder for oral intake, and solution form for intravenous and intramuscular injections.

Oral suspension is usually given for treating constipation and cholecystitis (inflammation of the gallbladder). It has a laxative effect. It is, therefore, useful for bowel cleansing in the case of diagnostic procedures, and in cases of poisoning.

The intravenous or intramuscular administration is prescribed for lowering blood pressure and dilating blood vessels. It has a diuretic property, and therefore, helps excrete the fluids from the body. It also lowers the uterine tone in pregnancy.

Magnesium intravenous drip therapy is prescribed for the following conditions in pregnancy:

  • Increased uterine tone
  • Hypertension
  • Preeclampsia associated with seizures
  • Swelling
  • Thrombosis
  • To induce sedative effect
  • Magnesium deficiency


  • Magnesium sulfate is not advisable during the first trimester.
  • Also, there is no proper evidence showing that it is completely safe during pregnancy.
  • It can only be taken upon doctor’s prescription.

Are there any side effects?

Magnesium therapy is only used for a short period of three to seven days. If it is a long-term treatment, it may accumulate in your body causing respiratory failure and hypoxia in the fetus. It may also subject calcium to a process of leaching from the fetal bone tissue causing fractures in the newborn during labor. You should stop taking it before labor (11).

Magnesium Citrate During Pregnancy

This is another salt of magnesium. It is FDA approved and falls under category C, which means there are not enough studies available to put it in a different category.

  • It is a saline laxative that improves the bowel movements, and also an osmotic laxative which means it retains water in the stools.
  • It is also prescribed to patients undergoing colonoscopy or other surgeries.
  • You should consult your doctor before using it as any medication during pregnancy, and it can only be used under doctor’s approval.

Frequently Asked Questions

1. What is the role of magnesium oxide during pregnancy?

Magnesium oxide is an FDA approved magnesium supplement that is safe to take in prescribed amounts. It is used as a supplement and laxative during pregnancy (12).

The US National Institutes of Health advises not to take it for a longer period without getting approval from the doctor (13).

2. Can you take magnesium hydroxide during pregnancy?

Magnesium hydroxide (milk of magnesia) is not approved by the FDA in the pregnancy category. There are no controlled studies regarding the usage of this drug during pregnancy. Though a laxative, it can only be taken under doctor’s supervision.

3. What are the other magnesium supplements the doctor usually suggests in pregnancy?

Magnesium malate and magnesium glycinate are two other supplements which are prescribed during pregnancy. All of these magnesium salts would only be given when the benefits outweigh the risks.

4. Is magnesium oil safe during pregnancy?

Magnesium oil is another safe option during pregnancy and helps in treating the symptoms of preeclampsia. The oil is absorbed through the skin, and it will not pass into the digestive tract. It can be used as a lotion, which you can leave on the skin. You can use 15ml to apply on the skin or add it to warm water for a body soak. About 120ml can be used for a bath. Unlike the oral magnesium salts with the laxative property, the oil will not cause any digestive stress.

Make sure to keep track of all the magnesium supplements you take during pregnancy so that you will not exceed the recommended daily limit. And always check with your doctor regarding any medications or supplements you are considering.

Do not forget to share your experiences with us in the below comment section.

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Rebecca Malachi

Rebecca is a pregnancy writer and editor with a passion for delivering research-based and engaging content in areas of fertility, pregnancy, birth, and post-pregnancy. She has been into health and wellness writing since 2010. She received her graduate degree in Biotechnology and Genetics from Loyola Academy, Osmania University and obtained a certification in ‘Nutrition and Lifestyle in Pregnancy’ from Ludwig... more