Preeclampsia, also written pre-eclampsia, is a condition during pregnancy when there is a sudden, sharp rise in blood pressure, swelling (edema) and albuminuria (excess protein albumin leaks into the urine). Swelling tends to occur in the face, hands and feet.
Preeclampsia is the most common complication that can occur during a pregnancy. It generally develops during the third trimester and affects about 1 in every 20 pregnancies.
In this article, we will cover various aspects of preeclampsia, its complications, diagnosis and treatment.
Contents of this article:
Fast facts on preeclampsia
Here are some key points about preeclampsia. More detail and supporting information is in the main article.
- Preeclampsia affects roughly 5% of pregnancies
- If preeclampsia is untreated, it can develop into eclampsia, a potentially life-threatening condition
- The two major early symptoms of preeclampsia are high blood pressure and protein in the urine
- Later symptoms include malaise, rapid weight gain and vomiting
- The exact causes of preeclampsia are not known but are likely to involve blood vessels in the placenta
- Some research implies that there is a genetic component to preeclampsia
- According to one study, traffic pollution might be connected to preeclampsia
- Other risk factors for preeclampsia include family history, age and obesity
- Antihypertensives are often prescribed to reduce blood pressure.
What is preeclampsia?
Preeclampsia affects 1 in 20 pregnancies.
Women in their first pregnancy have a higher risk of developing preeclampsia, as do patients with diabetes and mothers carrying twins. Some women have preeclampsia in every pregnancy; experts are not sure why.
If the preeclampsia remains untreated, it can develop to eclampsia, in which the mother can go into convulsions, coma and can even die. Complications from preeclampsia are extremely rare if the mother attends her pre-natal appointments.
Preeclampsia can have some long-term consequences for the developing baby. High blood pressure in pregnant women may affect the baby's thinking skills which can carry through for many years, researchers from the University of Helsinki, Finland, reported in the journal Neurology, October 2012.
Whether or not exercise is good for women at risk of preeclampsia has been a controversial subject for many years. Researchers from the University of North Carolina at Chapel Hill School of Nursing found that stretching exercises may help reduce the risk of preeclampsia.
Symptoms of preeclampsia
Early signs of preeclampsia include:
- Hypertension (high blood pressure)
- Proteinuria (protein in the urine)
In the majority of cases, the mother will not be aware of these signs, and will find out when the midwife, nurse, GP (general practitioner, primary care physician) or obstetrician picks them up during an antenatal visit.
Although between 10% and 15% of all pregnant women experience hypertension, it does not necessarily mean they have preeclampsia. The most telling sign is the presence of protein in the urine.
As the preeclampsia progresses, the mother can experience edema (fluid retention), with swelling in the hands, feet, ankles and face.
Swelling is a common part of pregnancy, especially during the third trimester, and tends to occur in the lower parts of the body, such as the ankles and feet. Symptoms are usually milder first thing in the morning, and build up during the day. This is not preeclampsia, in which edema occurs suddenly and tends to be much more severe.
Later on, the following signs and symptoms may develop:
- Blurry vision, sometimes seeing flashing lights
- Headaches, often severe
- Pain just below the ribs
- Rapid weight gain (caused by edema)
The main sign of preeclampsia in the fetus is poor growth, because the blood supply to the placenta is restricted.
Causes of preeclampsia
Experts are not sure why preeclampsia occurs. Most say that there is a problem with the proper development of the placenta, because the blood vessels that supply it are faulty.
How might the placenta affect blood pressure?
The mother's blood supply links to the unborn baby's via the placenta. All the baby's oxygen and nutritional requirements go through the placenta. The baby's waste products travel the opposite way, through the placenta, to the mother.
As the baby grows, the amount of blood that passes through the placenta increases.
In preeclampsia, the food supply to the placenta is inadequate; possibly because the placenta itself has not developed properly during the pregnancy.
The placenta may not have developed properly because early on in the pregnancy, tiny blood vessels (villi) which form within the placenta should eventually turn into arteries. If they do not transform fully into arteries, the placenta will not develop as it should because it is not receiving enough nutrients. Nobody knows why the blood vessels do not transform into proper arteries.
Preeclampsia is thought to be due to insufficiently formed placental blood vessels.
If the placenta is not functioning properly, the extra blood supply that should be pushing through from the mother will not go through, causing hypertension, swelling and possibly kidney problems. She cannot eliminate waste products fast enough and they build up in her blood, while certain vital proteins that should stay in the bloodstream leak into her urine, causing proterinuria.
An overabundance of a gene linked to the regulation of the body's immune system was discovered in the placentas of women who suffered preeclampsia during their pregnancy. The researchers, from North Carolina State University said that their discovery may lead the way to better screening and prenatal care.
Pregnant women who are exposed to traffic air pollution have a greater risk of developing preeclampsia compared to pregnant women of the same age who are not exposed, researchers from the University of California, Irvine, reported in Environmental Health Perspectives, June 2009 issue.
When CYP2J2 was inhibited in animal experiments, symptoms of preeclampsia improved.
CYP2J2 plays a major role in the production of EETs (epoxyeicosatrienoic acids) - metabolites which regulate blood pressure, vascular growth and inflammatory processes. EETs are beneficial for humans, but not when a woman has preeclampsia.
On the next page, we look at risk factors, diagnosis, treatment and complications of preeclampsia.