Preeclampsia

September 23, 2011

Preeclampsia, otherwise known as “toxemia,” is a disease unique to pregnancy that affects approximately 5-8% of all pregnant women. Preeclampsia is part of the spectrum of hypertensive disorders of pregnancy, which accounts for approximately 18% of all maternal deaths in the United States.

By definition, preeclampsia is unique to pregnancy and usually occurs after 20 weeks’ gestation. Preeclampsia has traditionally been diagnosed clinically with a triad of signs including two of the following three: edema (swelling), hypertension (high blood pressure), and proteinuria (protein in the urine). The edema is significant if it occurs in the face and hands (as opposed to legs and feet), but this has recently become the least important symptom in the diagnosis. Preeclampsia can be associated with a dramatic weight gain over a short period of time. Hypertension is defined as two blood pressure readings of greater than 140/90 taken in the seated position greater than 6 hr apart. Prior to 20 weeks’ gestation, an elevation in blood pressure is usually unrelated to the woman being pregnant, and preeclampsia is a disease that typically occurs later than 20 weeks’ gestation. Proteinuria is defined as >300 mg protein in a 24-hr collection of urine or greater than or equal to 1+ protein dipped on a clean catch urine.

Risks factors for developing preeclampsia include: first pregnancy; more than one fetus (twins, triplets, etc.); having had preeclampsia in a prior pregnancy; diabetes; molar pregnancies; chronic hypertension; systemic lupus erythematosus (SLE); kidney disease; obesity; older age; thrombophilias (blood clotting disorders); and family history. The exact etiology of preeclampsia is unclear, but we have some clues. For example, preeclampsia is not only unique to pregnancy, but it is also unique to the placenta versus the fetus. This is demonstrated by the fact that molar pregnancies (without fetal tissue) are at high risk for preeclampsia as well as pregnancies complicated by abnormal placentas. There is evidence that changes of preeclampsia start as early as the first trimester of pregnancy with abnormal blood vessels in the early placental tissue. This may predispose a patient to release of “toxins,” hence the older term toxemia. The only cure for preeclampsia is delivery or evacuation of the uterus. However, preeclampsia may be temporized depending on the severity of the disease and the health of the mother and fetus.

Preeclampsia is stratified into mild and severe. Severe preeclampsia is also subdivided into severe preeclampsia based on blood pressure (>160/110 mm Hg as measured with a blood pressure cuff) or proteinuria (>5g in 24 hr), HELLP syndrome (hemolysis [the breakdown of red blood cells], elevated liver enzymes, and low platelets), and eclampsia. Other indicators of severe preeclampsia are maternal symptoms and fetal symptoms. Maternal signs and symptoms are headache, blurry vision or flashing lights, mid or right upper quadrant abdominal pain, oliguria (low urine output), pulmonary edema (water on the lungs), heart failure, and kidney failure. Fetal signs are oligohydramnios (low amniotic fluid) and intrauterine growth restriction (failure to grow appropriately in the uterus).

Eclampsia is perhaps the most severe form of preeclampsia and is defined by the presence of seizures with no other known seizure etiology. Prophylaxis against seizures is typically administered for the severe preeclamptic patient and often the mild preeclamptic patient. The most common and most effective seizure prophylaxis (preventive) is intravenous magnesium sulfate. The standard dose is 4 g IV (intravenous) over 20 min and then 2 g IV per hour. Seizures are most likely to occur during labor and in the first 24 hr after delivery. The most commonly associated prodromal (warning) symptoms of an eclamptic seizure are a headache and visual changes. Seizures have also been reported up to 2 weeks postpartum but if they occur more than 48 hr postpartum, other reasons for the seizure must be considered.

Management of preeclampsia and eclampsia depends on the severity as stated above. Eclampsia and HELLP syndrome necessitate delivery regardless of gestational age. Mild preeclampsia can be monitored closely until either the fetus’ lungs are mature or a gestational age of 36 weeks is reached. Severe preeclampsia should also be delivered expeditiously unless the diagnosis is based on elevated blood pressure that can be controlled with medication or based solely on proteinuria. Patients who have severe preeclampsia but are delaying delivery due to fetal immaturity should be managed at a tertiary care center as an inpatient with daily maternal and fetal testing.

SEE ALSO: Diabetes, Hypertension, Preconception care, Pregnancy, Renal disease, Seizures, Systemic lupus erythematosus

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