What is it?
Preeclampsia is a condition of pregnancy marked by high blood pressure and excess protein in your urine after 20 weeks of pregnancy. Preeclampsia often causes only modest increases in blood pressure. Left untreated, however, preeclampsia can lead to serious — even fatal — complications for both you and your baby.
If you have preeclampsia, the only cure is delivery of your baby. If you're diagnosed with preeclampsia too early in your pregnancy for delivery to be an option, you and your doctor need to allow your baby more time to mature, without putting you or your baby at risk of serious complications.
Preeclampsia can develop gradually but often attacks suddenly, after 20 weeks of pregnancy. Preeclampsia may range from mild to severe. If your blood pressure was normal before your pregnancy, signs and symptoms of preeclampsia may include:
- High blood pressure (hypertension) — 140/90 millimeters of mercury (mm Hg) or greater — documented on two occasions, at least six hours but no more than seven days apart
- Excess protein in your urine (proteinuria)
- Severe headaches
- Changes in vision, including temporary loss of vision, blurred vision or light sensitivity
- Upper abdominal pain, usually under your ribs on the right side
- Nausea or vomiting
- Decreased urine output
- Sudden weight gain, typically more than 2 pounds (0.9 kilograms) a week
Swelling (oedema), particularly in your face and hands, often accompanies preeclampsia. Swelling isn't considered a reliable sign of preeclampsia, however, because it also occurs in many normal pregnancies.
Preeclampsia used to be called toxemia because it was thought to be caused by a toxin in a pregnant woman's bloodstream. This theory has been discarded, but researchers have yet to determine what causes preeclampsia. Possible causes may include:
- Insufficient blood flow to the uterus
- Damage to the blood vessels
- A problem with the immune system
- Poor diet
Other high blood pressure disorders during pregnancy
Preeclampsia is classified as one of four high blood pressure disorders that can occur during pregnancy. The other three are:
- Gestational hypertension. Women with gestational hypertension have high blood pressure, but no excess protein in their urine. Some women with gestational hypertension eventually develop preeclampsia.
- Chronic hypertension. Chronic hypertension is high blood pressure that appears before 20 weeks of pregnancy or lasts more than 12 weeks after delivery. Usually, chronic hypertension was present — but not detected — before pregnancy.
- Preeclampsia superimposed on chronic hypertension. This term describes women who have chronic high blood pressure before pregnancy and then develop worsening high blood pressure and protein in the urine during pregnancy.
Preeclampsia develops only during pregnancy. Risk factors include:
- History of preeclampsia. A personal or family history of preeclampsia increases your risk of developing the condition.
- First pregnancy. The risk of developing preeclampsia is highest during your first pregnancy or your first pregnancy with a new partner.
- Age. The risk of preeclampsia is higher for pregnant women younger than 20 and older than 40.
- Obesity. The risk of preeclampsia is higher if you're obese.
- Multiple pregnancy. Preeclampsia is more common in women who are carrying twins, triplets or other multiples.
- Prolonged interval between pregnancies. This seems to increase the risk of preeclampsia.
- Gestational diabetes. Women who develop gestational diabetes have a higher risk of developing preeclampsia as the pregnancy progresses.
- History of certain conditions. Having certain conditions before you become pregnant — such as chronic high blood pressure, migraine headaches, diabetes, kidney disease, rheumatoid arthritis or lupus — increases the risk of preeclampsia.
Other associated factors
Other factors that may be associated with a higher risk of preeclampsia include:
- Having other health conditions. There's some evidence that both urinary tract infections and periodontal disease during pregnancy are associated with an increased risk of preeclampsia, which may indicate that antibiotics could play a role in prevention of preeclampsia. More study is needed.
- Vitamin D insufficiency. There's also some evidence that insufficient vitamin D intake increases the risk of preeclampsia, and that vitamin D supplements in early pregnancy could play a role in prevention. More study is needed.
- High levels of certain proteins. Pregnant women who had high levels of certain proteins in their blood or urine have been found to be more likely to develop preeclampsia than are other women. These proteins interfere with the growth and function of blood vessels — lending evidence to the theory that preeclampsia is caused by abnormalities in the blood vessels feeding the placenta. Although more research is needed, the discovery suggests that a blood or urine test may one day serve as an effective screening tool for preeclampsia.
Most women with preeclampsia deliver healthy babies. The more severe your preeclampsia and the earlier it occurs in your pregnancy, however, the greater the risks for you and your baby. Preeclampsia may require induced labor and delivery by Caesarian section. Complications of preeclampsia may include:
- Lack of blood flow to the placenta. Preeclampsia affects the arteries carrying blood to the placenta. If the placenta doesn't get enough blood, your baby may receive less oxygen and fewer nutrients. This can lead to slow growth, low birth weight, preterm birth and breathing difficulties for your baby.
- Placental abruption. Preeclampsia increases your risk of placental abruption, in which the placenta separates from the inner wall of your uterus before delivery. Severe abruption can cause heavy bleeding, which can be life-threatening for both you and your baby.
- HELLP syndrome. HELLP — which stands for hemolysis (the destruction of red blood cells), elevated liver enzymes and low platelet count — syndrome can rapidly become life-threatening for both you and your baby. Symptoms of HELLP syndrome include nausea and vomiting, headache, and upper right abdominal pain. HELLP syndrome is particularly dangerous because it can occur before signs or symptoms of preeclampsia appear.
- Eclampsia. When preeclampsia isn't controlled, eclampsia — which is essentially preeclampsia plus seizures — can develop. Symptoms of eclampsia include upper right abdominal pain, severe headache, vision problems and change in mental status, such as decreased alertness. Eclampsia can permanently damage your vital organs, including your brain, liver and kidneys. Left untreated, eclampsia can cause coma, brain damage and death for both you and your baby.
- Cardiovascular disease. Having preeclampsia may increase your risk of future cardiovascular disease.
Pre-eclampsia usually shows up during a routine prenatal blood pressure check and urine test. The diagnosis depends on the presence of high blood pressure and protein in your urine after 20 weeks of pregnancy. Certain markers in your blood and urine may be indications of preeclampsia. That's why it's essential to seek early and regular prenatal care throughout your pregnancy.
A blood pressure reading in excess of 140/90 mm Hg clearly is abnormal in pregnancy. However, a single high blood pressure reading doesn't mean you have preeclampsia. If you have one reading in the abnormal range — or a reading that's substantially higher than your usual blood pressure — your doctor will closely observe your numbers. You may also be asked to come in for additional blood pressure readings and urinary protein measurements.
If you're diagnosed with preeclampsia, your doctor may recommend additional tests, including:
- Blood tests. These can determine how well your liver and kidneys are functioning and whether your blood has a normal number of platelets — the cells that help blood clot.
- Prolonged urine collection test. Urine samples taken over at least 12 hours and up to 24 hours can quantify how much protein is being lost in the urine, an indication of the severity of preeclampsia.
- Fetal ultrasound. Your doctor may also recommend close monitoring of your baby's growth, typically through ultrasound. This test directs high-frequency sound waves at the tissues in your abdominal area. These sound waves bounce off the curves and variations in your body, including your baby. The sound waves are translated into a pattern of light and dark areas — creating images of your baby on a monitor that can be recorded electronically or on film for a look at the inside of your uterus.
- Nonstress test or biophysical profile. These make sure your baby is getting enough oxygen and nourishment. A nonstress test is a simple procedure that checks how your baby's heart rate reacts when your baby moves. Your baby is doing fine if the heart rate increases at least 15 beats a minute for at least 15 seconds twice in a 20-minute period. A biophysical profile combines an ultrasound with a nonstress test to provide more information about your baby's breathing, tone, movement and the volume of amniotic fluid in your uterus.