Magnesium Sulfate In Pregnancy

Magnesium Sulfate In Pregnancy


Magnesium Sulfate During Pregnancy

Pregnancy requires constant medical observation in every stage. Magnesium sulfate is prescribed quite often during pregnancy for decreasing uterine tonus and preventing premature birth. Let us consider the benefits of this drug.

Magnesium Sulfate Properties

Magnesium sulfate is a medication in the form of white powder for preparing oral suspension and in the form of solution for intramuscular and intravenous injections. The method of application of the drug depends on the indications.

Magnesium sulfate is used orally for treating cholecystitis and constipation. It produces a laxative and choleretic effect. It is also applied for bowel cleansing before diagnostic procedures and in cases of poisoning by the salts of heavy metals.

Magnesium sulfate administered via the intravenous or intramuscular route dilates blood vessels and lowers blood pressure. It can also produce a diuretic effect, promoting the excretion of fluids from the body. Magnesium reduces the uterine tonus during pregnancy.


Magnesium intravenous (IV) drip therapy may be prescribed during pregnancy in cases of:

  • hypertension;
  • increased uterine tonus for preventing miscarriage or premature birth;
  • swelling;
  • preeclampsia characterized by seizures;
  • predisposition to thrombosis;
  • deficiency of magnesium in the body;
  • for producing a sedative effect.


Contraindications for using magnesium sulfate:

  • hypotension (low blood pressure);
  • bradycardia (slow heart rate);
  • chronic renal disease;
  • individual intolerance;
  • diseases of the gastrointestinal tract in the period of exacerbation;
  • pre-birth period.

Magnesium sulfate is not used in the early stages of pregnancy (first trimester). The researches of the magnesium effect on fetus development in early stages have not been conducted. Therefore, there is no positive evidence that the drug is completely safe for use during this period of pregnancy. In practice, doctors prescribe magnesium sulfate to the patients with high uterine tonus. In some cases, the use of magnesium can be the only means to prevent a miscarriage.

Side Effects

Magnesium Sulfate During Pregnancy

The doctor should warn you about the possible side effects during the use of magnesium. If you experience any of the below symptoms, you should consult your doctor about the further treatment with magnesium.

The use of magnesium sulfate during pregnancy may cause the following side effects:

  • headaches;
  • nausea and vomiting;
  • general weakness and fatigue;
  • arrhythmia and bradycardia;
  • depression of the respiratory center;
  • thirst and excessive sweating;
  • reduced tendon reflexes;
  • speech disorders;
  • increased anxiety.

In cases of the sudden drop of blood pressure, difficulty in breathing, or slowing of heart rate, treatment with magnesium sulfate should be cancelled immediately.

Dosage of Magnesium Sulfate in Pregnancy

Intramuscular magnesium sulfate injections are rarely applied during pregnancy, as these injections are very painful and may leave bumps. During treatment, a 25 % solution of magnesium sulfate is administered by the IV drip. A single dose is 20 ml. Duration of treatment is determined depending on the condition of a pregnant woman and the existing complications.

The drug is heated to body temperature and slowly infused into the vein via the drip with a long needle. A quick administration of the drug can trigger a sudden decline in pressure that in turn may lead to hypoxia (oxygen starvation) of the fetus.

Interaction With Other Drugs

Avoid taking magnesium sulfate together with dietary supplements and medications containing calcium (calcium chloride, calcium gluconate). Calcium neutralizes the magnesium action in the body.

Magnesium sulfate reduces the absorption of tetracyclines and fluoroquinolones, lowers the action of tobramycin and streptomycin and is incompatible with alcohol. All these substances are forbidden during pregnancy, as well as alcohol.

Magnesium Effect on Fetus and Labor

The fundamental clinical researches of the magnesium sulfate effect during pregnancy have not been conducted. However, the extensive use of the drug in medicine is considered a powerful argument in favor of its safety. Pregnant women, who enter the hospital for bed rest, are often prescribed magnesium sulfate therapy.

As any drug, magnesium sulfate is prescribed to pregnant women in cases when the expected therapeutic effect is greater than the potential risk to the fetus. An increased uterine tone is considered more dangerous than the side effects of the drug. In some cases, the use of magnesium IV drip therapy can be the only way to save the pregnancy.

In the late stages of pregnancy, magnesium therapy is commonly used for a short period that is considered to be safe. During long-term treatment the drug may accumulate in the body and cause hypoxia and respiratory failure in fetus. Moreover, a prolonged use of magnesium may leach calcium from the bone tissue of the fetus that leads to fractures in a baby during labor.

According to the study of American researchers, which was conducted on the basis of the registered cases, women who had received magnesium for 10 weeks during pregnancy had their babies born with skeletal abnormalities, fractures of ribs and deficiency of calcium and phosphorus in blood. Therefore, it was established that the required time for magnesium sulfate IV drip therapy in pregnancy should be 3 to 5 days, maximum to 7 days.

The use of magnesium sulfate should be canceled before labor. The drug is excreted from the body within a few hours. After that time, the drug does not produce any effect on labor process.

Safe Use of Magnesium Sulfate in Pregnancy

One Comment

  • Demi says:

    my grandaughter has been in hospital at 30 weeks pregnant and has had severe headaches constant vomiting and very low blood presure the doctor has put her on an iv magnesium drip why would they do this can this be harmful to her or baby

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