Treatment of Preeclampsia: Magnesium Sulfate Therapy

Treatment of Preeclampsia: Magnesium Sulfate Therapy

What Is Preeclampsia?

Preeclampsia is a complication some women experience in pregnancy. It often occurs about 20 weeks into a pregnancy. The major signs of preeclampsia are high blood pressure and organs not working normally. An example of these signs is excess protein in urine (proteinuria).

The exact causes of preeclampsia are unknown. Experts think it’s caused by problems with the blood vessels that connect to a pregnant woman’s placenta, the organ inside which babies grow.

During the early stages of pregnancy, new blood vessels begin to form. These new blood vessels may develop abnormally for several different reasons, including:

  • inadequate blood flow to the uterus
  • blood vessel damage
  • immune system problems
  • genetic factors

These abnormal blood vessels restrict the amount of blood that can move to the placenta. This can cause a mother’s blood pressure to increase.

If left untreated, preeclampsia can be life-threatening to both the mother and her baby. Because it involves problems with the placenta, the only real cure for a mother with preeclampsia is delivering her baby.

A diagnosis of preeclampsia early in a woman’s pregnancy can be tricky. The baby needs time to grow inside its mother, but both the mother and the baby need to avoid any serious complications. In this case, your doctor may prescribe magnesium sulfate.

Magnesium sulfate therapy is used to prevent seizures in women with preeclampsia. It can also help prolong a pregnancy for up to two days. This allows drugs that speed up your baby’s lung development to take effect.

What Are the Symptoms of Preeclampsia?


In some women, preeclampsia develops gradually without any symptoms.

High blood pressure, the major sign of preeclampsia, usually occurs suddenly. This is why it’s important for expectant mothers to monitor their blood pressure closely, especially during the early part of their pregnancy. A blood pressure reading of 140/90 millimeters of mercury or higher, taken at two separate times at least four hours apart, is considered abnormal.

Besides high blood pressure, other signs or symptoms of preeclampsia include:

  • excess protein in urine (proteinuria)
  • decreased amount of urine
  • low platelet count in blood (thrombocytopenia)
  • intense headaches
  • vision problems such as loss of vision, blurry vision, and sensitivity to light
  • pain in the upper abdomen, usually under the ribs on the right side
  • vomiting or nausea
  • weakened liver function
  • trouble breathing (due to fluid in the lungs)
  • rapid weight gain and swelling, especially in the face and hands

If a doctor suspects a woman has preeclampsia, they will perform blood and urine tests to make a diagnosis.

What Are the Possible Complications?

Complications Icon

A woman is more likely to have complications if she develops preeclampsia early in her pregnancy, and has noticeable symptoms. In some cases, doctors must perform induced labor and delivery or a caesarean section (C-section) to remove the baby from its mother’s body. This will stop preeclampsia from progressing.

If left untreated, complications may develop. Some complications of preeclampsia include:

  • a lack of oxygen to the placenta: can cause slow growth, low birth weight, or preterm (early) birth of the baby
  • placental abruption: the separation of the placenta from the uterus wall, which can cause severe bleeding and damage to the placenta
  • HELLP syndrome: causes hemolysis (loss of red blood cells), elevated liver enzymes, and low blood platelet count, resulting in organ damage
  • eclampsia: preeclampsia with seizures

Women who develop preeclampsia face an increased risk of heart and blood vessel disease. Their risk of preeclampsia in future pregnancies also increases. Mothers who have had preeclampsia have a 16 percent chance of developing it again in a future pregnancy.

How Does Magnesium Sulfate Therapy Treat Preeclampsia?


The only cure for a pregnant woman with preeclampsia is delivering her baby. Waiting to deliver can increase a woman’s risk of complications. If it’s too early in her pregnancy, she may have to wait until her baby is large enough to be born.

Doctors usually recommend women with preeclampsia come in more often for prenatal visits. They may perform more frequent blood and urine tests. They may also prescribe:

  • medications to lower blood pressure
  • corticosteroids (can help mature baby’s lungs and improve mother’s health)
  • hospitalization

In severe cases of preeclampsia, doctors often recommend antiseizure medications. One such medication is called magnesium sulfate. Magnesium sulfate is a mineral that reduces seizure risks in women with preeclampsia. A healthcare provider will give the medication intravenously, or into the body through a vein. Sometimes, it’s also used to prolong pregnancy for up to two days. This allows time for corticosteroid drugs to improve the baby’s lung function.

Magnesium sulfate usually takes effect immediately. It’s normally given until about 24 hours after a woman delivers her baby.

Are There Any Side Effects?

Risk Factors

Magnesium sulfate can be beneficial to some women with preeclampsia. But there is a risk of magnesium overdose, called magnesium toxicity. Taking too much magnesium can be life-threatening to both mother and child. In women, the most common symptoms include:

  • nausea, diarrhea, or vomiting
  • big drops in blood pressure
  • slow or irregular heartbeat
  • breathing problems
  • deficiencies in minerals other than magnesium (especially calcium)
  • confusion or fogginess
  • coma
  • heart attack
  • kidney damage

In a baby, magnesium toxicity can cause low muscle tone and “floppiness.” This is caused by poor muscle control and low bone density. These conditions can put a baby at greater risk of injuries, such as bone fractures, and even death.

Doctors can treat magnesium toxicity by:

  • pumping a woman’s stomach
  • giving fluids
  • providing breathing support
  • performing dialysis

It’s best to prevent magnesium toxicity from happening in the first place. Doctors should closely monitor pregnant women taking magnesium sulfate. They should also ask women how they’re feeling, monitor their breathing, and check their reflexes often.

What Is the Outlook?


Your doctor may continue to give you magnesium sulfate throughout your delivery. Your blood pressure should return to a normal level within 12 days of delivery.

The best way to prevent complications from preeclampsia is an early diagnosis. Go to your prenatal care visits and always tell your doctor about any new symptoms.

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