The exact cause of preeclampsia is unknown. However, there are numerous theories about the condition’s cause. Theoretical causes include:

• Uterine ischemia/underperfusion. Inadequate blood flow to the uterus.
  
  
• Prostacyclin/thromboxane imbalance. A disruption in the balance of hormones that control the diameter of the blood vessels.
  
  
• Endothelial activation and dysfunction. Damage to the lining of the blood vessels that controls the diameter of the blood vessels (keeping fluid and protein inside the blood vessels) and prevents blood from clotting.
  
  
• Calcium deficiency. A lack of calcium, a substance that helps maintain vasodilation (widening of the blood vessels).
  
  
• Immunological activation. The immune system mistakenly tries to fix damage to a blood vessel that has not occurred, causing actual injury.
  
  
• Hemodynamic vascular injury. Blood vessel injury caused by too much blood flow.
  
  
• Preexisting maternal conditions (e.g., diabetes, lupus, sickle cell disorder, hyperthyroidism, kidney disorder, undiagnosed high blood pressure).
  
  
• Poor diet (e.g., not enough protein, excessive protein, not enough antioxidants).
  
  
• High body fat.
  
  
• Insufficient magnesium oxide and vitamin B6.
  
  
• Genetic tendency.

Although none of these theories have been proven, researchers have identified a number of factors that make a woman more likely to develop the condition. Risk factors for preeclampsia include:

• Personal medical history. Women who have had preeclampsia during a prior pregnancy have an increased risk of developing the condition in later pregnancies. According to the National Institutes of Health (NIH), the risk of recurrent preeclampsia in later pregnancies is approximately 33 percent. Women with a personal history of preeclampsia are encouraged to discuss subsequent pregnancies with their physicians, in order to discuss the possible risks and weigh the potential options. 
  
  
• Family history. Women with a first degree relative (e.g., mother, sister) who had preeclampsia are more likely to develop the condition.
  
  
• First pregnancy. There is an increased risk of developing the condition in a woman’s first pregnancy (excluding miscarriages). The risk is also increased in a woman’s first pregnancy with a new partner or first pregnancy in 10 years or more.
  
  
• Age. Women under age 18 and over age 40 at the time of pregnancy are more likely to develop the condition.
  
  
• Obesity. Women with a pre-pregnancy body mass index (BMI) greater than 30 are at an increased risk of developing the condition.
  
  
• Multiple pregnancy. Women carrying two or more babies are more likely to develop preeclampsia.
  
  
• History of certain conditions. Having certain conditions before pregnancy can increase a woman’s risk of developing preeclampsia. These conditions include chronic high blood pressure, diabetes, kidney disease, polycystic ovarian syndrome, sarcoidosis, multiple sclerosis and connective tissue disease (e.g., rheumatoid arthritis, lupus).
  
  
• Race. African-American women are more likely to develop the condition.