Preeclampsia sometimes develops without any symptoms. High blood pressure may develop slowly, but more commonly it has a sudden onset. Monitoring your blood pressure is an important part of prenatal care because the first sign of preeclampsia is commonly a rise in blood pressure. Blood pressure that is 140/90 millimeters of mercury (mm Hg) or greater — documented on two occasions, at least four hours apart — is abnormal.
Other signs and symptoms of preeclampsia may include:
- Excess protein in your urine (proteinuria) or additional signs of kidney problems
- 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
- Decreased levels of platelets in your blood (thrombocytopenia)
- Impaired liver function
- Shortness of breath, caused by fluid in your lungs
Sudden weight gain and swelling (edema) — particularly in your face and hands — often accompanies preeclampsia. But these things also occur in many normal pregnancies, so they're not considered reliable signs of preeclampsia.
When to see a doctor
Make sure you attend your prenatal visits so that your care provider can monitor your blood pressure. Contact your doctor immediately or go to an emergency room if you have severe headaches, blurred vision, severe pain in your abdomen or severe shortness of breath.
Because headaches, nausea, and aches and pains are common pregnancy complaints, it's difficult to know when new symptoms are simply part of being pregnant and when they may indicate a serious problem — especially if it's your first pregnancy. If you're concerned about your symptoms, contact your doctor.
The exact cause of preeclampsia is unknown. Experts believe it begins in the placenta — the organ that nourishes the fetus throughout pregnancy. Early in pregnancy, new blood vessels develop and evolve to efficiently send blood to the placenta. In women with preeclampsia, these blood vessels don't seem to develop properly. They're narrower than normal blood vessels and react differently to hormonal signaling, which limits the amount of blood that can flow through them.
Causes of this abnormal development may include:
- Insufficient blood flow to the uterus
- Damage to the blood vessels
- A problem with the immune system
- Certain genes
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 or other signs of organ damage. Some women with gestational hypertension eventually develop preeclampsia.
- Chronic hypertension. Chronic hypertension is high blood pressure that was present before pregnancy or that occurs before 20 weeks of pregnancy. But because high blood pressure usually doesn't have symptoms, it may be hard to determine when it began.
- Chronic hypertension with superimposed preeclampsia. This condition occurs in women who have chronic high blood pressure before pregnancy who then develop worsening high blood pressure and protein in the urine or other health complications during pregnancy.
Preeclampsia develops only as a complication of pregnancy. Risk factors include:
- History of preeclampsia. A personal or family history of preeclampsia significantly raises your risk of preeclampsia.
- First pregnancy. The risk of developing preeclampsia is highest during your first pregnancy.
- New paternity. Each pregnancy with a new partner increases the risk of preeclampsia over a second or third pregnancy with the same partner.
- Age. The risk of preeclampsia is higher for pregnant women 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.
- Interval between pregnancies. Having babies less than two years or more than 10 years apart leads to a higher risk of preeclampsia.
- History of certain conditions. Having certain conditions before you become pregnant — such as chronic high blood pressure, migraine headaches, type 1 or type 2 diabetes, kidney disease, a tendency to develop blood clots, or lupus — increases your risk of preeclampsia.
The more severe your preeclampsia and the earlier it occurs in your pregnancy, the greater the risks for you and your baby. Preeclampsia may require induced labor and delivery. Surgical delivery (cesarean section or C-section) isn't always advantageous unless other problems are present, such as a baby in breech presentation, or if a speedy delivery is necessary. If you have severe preeclampsia or you're at less than 30 weeks gestation, a C-section may be necessary.
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 or preterm birth. Prematurity can lead to breathing problems for the 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 and damage to the placenta, 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 represents damage to several organ systems. On occasion, it may develop suddenly, even before high blood pressure is detected.
- Eclampsia. When preeclampsia isn't controlled, eclampsia — which is essentially preeclampsia plus seizures — can develop. Symptoms that suggest imminent eclampsia include upper right abdominal pain, severe headache, vision problems and change in mental status, such as decreased alertness. Because eclampsia can have serious consequences for both mom and baby, delivery becomes necessary, regardless of how far along the pregnancy is.
- Cardiovascular disease. Having preeclampsia may increase your risk of future heart and blood vessel (cardiovascular) disease. The risk is even greater if you've had preeclampsia more than once or you've had a preterm delivery. To minimize this risk, after delivery try to maintain your ideal weight, eat a variety of fruits and vegetables, exercise regularly, and don't smoke.
Researchers continue to study ways to prevent preeclampsia, but so far, no clear strategies have emerged. Eating less salt, changing your activities, restricting calories, or consuming garlic or fish oil doesn't reduce your risk. Increasing your intake of vitamins C and E hasn't been shown to have a benefit, and the research into vitamin D is ongoing.
In certain cases, however, you may be able to reduce your risk of preeclampsia with:
- Low-dose aspirin. If you had preeclampsia in a previous pregnancy that resulted in delivery before 34 weeks' gestation or you had preeclampsia in more than one previous pregnancy, your doctor may recommend a daily low-dose aspirin — between 60 and 81 milligrams — beginning late in your first trimester.
- Calcium supplements. In some populations, women who have calcium deficiency before pregnancy — and who don't get enough calcium during pregnancy through their diets — might benefit from calcium supplements to prevent preeclampsia. However, it's unlikely that women from the United States or other developed countries would have calcium deficiency to the degree that calcium supplements would benefit them.
It's important that you don't take any medications, vitamins or supplements without first talking to your doctor.
Before you become pregnant, especially if you've had preeclampsia before, it's a good idea to be as healthy as you can be. Lose weight if you need to, and make sure other conditions, such as diabetes, are well-managed.
Once you're pregnant, take care of yourself — and your baby — through early and regular prenatal care. If preeclampsia is detected early, you and your doctor can work together to prevent complications and make the best choices for you and your baby.