Pregnancy-induced hypertension, often called PIH, affects between 10 to 15 percent of women during their first pregnancy and 7 percent in subsequent pregnancies, obstetrician Dr. Ashley Hill reports on OBGYN.net. The terms gestational hypertension, PIH, pregnancy-induced hypertension and toxemia all refer to the same condition, GYNOB.com explains. Signs of severe PIH include high blood pressure, upper right quadrant abdominal pain, edema, protein in the urine and exaggerated reflex responses. Pre-existing hypertension differs from PIH, which can cause mental changes, blurred vision, headache and seizures. Pregnancy-induced hypertension may require treatment with magnesium sulfate to prevent seizures.
Purpose
Magnesium sulfate acts as a muscle relaxant, which decreases the risk of seizures. Seizures occur because of swelling in the brain. Giving magnesium supplements during pregnancy does not prevent PIH, Liane Beck, M.D., of Emory Family Medicine explains. Magnesium sulfate doesn't reduce blood pressure levels, but may prevent premature separation of the placenta from the uterine wall, a pregnancy complication called an abruption.
Administration
Magnesium sulfate is usually given intravenously in the hospital, so a woman can receive constant monitoring. Continuous infusion of a dose large enough to decrease deep tendon reflexes follows a "loading dose" of 4 to 6 grams given rapidly. Magnesium sulfate is continued until 24 hours after delivery or after the last seizure. Monitoring serum magnesium levels ensures a therapeutic dose and helps avoid toxicity. Serum magnesium levels should fall between 4 and 7 milligrams per deciliter, Dr. Beck says.
Side Effects
Side effects of magnesium sulfate include drowsiness, weakness, loss of deep tendon reflexes, headache, nausea and vomiting, slurred speech, flushing and slowed breathing. Pregnant women receiving magnesium sulfate have their deep tendon reflexes, blood pressure and respiration rate evaluated frequently during administration. Because magnesium is excreted in the urine, urine output is also carefully assessed, because a decrease in urine output can result in excessive amounts of magnesium in the blood.
Benefits
Magnesium sulfate can prevent seizures that lead to fetal or maternal brain damage or death. Administration of magnesium sulfate in women with severe PIH cuts the risks of seizures by 50 percent, the University of Michigan Health System reports.
Risks
Magnesium toxicity can occur when a pregnant woman receives this drug. Symptoms include maternal respiratory arrest or complete loss of deep tendon reflexes. Fetal side effects include flaccidity and respiratory distress at the time of delivery, or fluid accumulation in the lungs called pulmonary edema.
