What is the cause of preeclampsia?

 

Scientists believe that preeclampsia is caused by the mother's placenta, cardiovascular system and immune system.

​

During normal pregnancy, the mother’s body undergoes many changes to adapt to pregnancy. This includes the development of the placenta and increased demands on the mom's cardiovascular system to provide proper levels of blood to supply the growing placenta and baby. The placenta and cardiovascular system coordinate during pregnancy by sending protein and other molecular signals to each other to guide these pregnancy changes.

​

Scientists believe that preeclampsia develops due to a breakdown in communication between the placenta and the rest of mom's body.

 

The placentas of most women with preeclampsia look and act differently than placentas of pregnant women who have healthy pregnancies. In more scientific terms, the anatomy and physiology of the placenta is typically abnormal in women with preeclampsia. 

​

Due to these placental abnormalities, the placenta of women with preeclampsia releases abnormal levels of proteins that then enter the mom's circulation and interact with her blood vessels and heart. These proteins from the placenta then interact with the inner cell layer of mom's blood vessels, known as endothelial cells, and can cause damage to these cells. Abnormal signaling by the placenta, damage to the endothelial cells, or a combination of both are thought to cause the symptoms associated with preeclampsia. 

​

Women who go on to be diagnosed with preeclampsia have higher blood pressures even at 10-17 weeks of pregnancy, when compared to women who continue to have normal blood pressure levels. When compared to pregnant women with normal blood pressure, women with preeclampsia show abnormal levels of resistance in their blood vessels (total peripheral resistance) and amount of blood pumped with each heart beat (cardiac output).

​

Read here for a more detailed article about the causes of preeclampsia.

​

​

Risk factors for preeclampsia

 

A number of risk factors for preeclampsia have been identified, including factors that relate to mom's placenta, cardiovascular system and immune system. These include:

​

• First pregnancy or first pregnancy with new partner

• Obesity

• Advanced maternal age​

• Ethnicity

• Twin birth

• In vitro fertilization

• History of preeclampsia in previous pregnancy

• Family history of preeclampsia

• Family history of early-onset cardiovascular disease

• Pre-existing cardiovascular or kidney disease

​

​

Symptoms of preeclampsia

 

Preeclampsia is associated with a range of symptoms, including:

​

• Headaches

• Dizziness

• Difficulty breathing

• Swelling & weight gain

• Pain in upper abdomen 

• Blurred vision or other changes in eyesight

• Nausea & vomiting

​

​

Testing & investigations for preeclampsia

 

Clinical testing can help to identify women who are at higher risk of developing preeclampsia, in addition to assessing the clinical risk factors (listed above). Doppler ultrasound can determine if pregnant woman have abnormal placental structure or function, which can indicate higher risk of severe preeclampsia.

​

Some hospitals now offer blood tests that can measure levels of proteins produced by the placenta in the mom's blood. Levels of these proteins in the mom's blood, including levels of placental growth factor, are highly predictive of preeclampsia and provide doctors with insight into how the mom's placenta is functioning. 

​

Read more here to learn about placental growth factor testing for preeclampsia screening.

​

Blood pressure monitoring is a standard practice for pregnant women in Canada and should be measured regularly at clinical appointments. High blood pressure is defined as:

​

• Non-severe - systolic blood pressure between 140-159 mmHg and/or diastolic blood pressure over 90-109 mmHg

• Severe - systolic blood pressure over 160 mmHg and/or diastolic blood pressure over 110 mmHg

​

If pregnant women have high blood pressure, they will also be checked for other symptoms of organ injury to determine if a women has gestational hypertension or preeclampsia. This typically includes testing urine for signs of kidney injury and testing blood for signs of other organ injury. Pregnant women with preeclampsia will show signs of organ injury, usually proteinuria (kidney damage). 

​

Doctors will check for evidence of:

​

• Proteinuria: check for high protein levels in the urine

• Renal insufficiency: check for high creatinine levels in the blood

• Thrombocytopenia: check for low platelet levels in the blood

• Impaired liver function: check for high liver enzyme levels in the blood

• Pulmonary edema: ask women about symptoms

• Cerebral or visual disturbances: ask women about symptoms

​

Doctors will also monitor the baby to ensure that growth and development are normal. This includes fetal heart rate, blood flow through the umbilical cord and blood flow in the brain. Studies have shown that pregnant women with hypertension tend to have smaller babies, compared to pregnant women with normal blood pressure. These investigations will let doctors know if the baby is being impacted by mom’s high blood pressure and if early delivery should be considered to ensure the health of the baby​.