Pre-eclampsia is a condition that affects around 5% of all pregnant women. The exact cause of this condition is not fully understood. However, there are several hypotheses concerning the development of the condition, which is thought to involve a problem with the placenta.

Some of the possible causes and risk factors in pre-eclampsia include:

• Inadequate blood supply to the placenta. This could be caused by a range of factors such as a malformed or damaged placenta or high blood pressure in the mother causing damage to the blood vessels of the placenta. High blood pressure also damages the blood vessels in the kidneys which can lead to the presence of proteins in the urine or proteinuria.
• Derangement of the maternal immune system causing rejection of the placenta.
• First pregnancies, especially in younger (teenage mothers) or older mothers (nearing or over 40 years).
• A gap of more than 10 years between two pregnancies
• A history of preeclampsia in previous pregnancies
• Women with a first degree female relative such as a mother or sister who has had preeclampsia are at a greater risk of this condition
• Women carrying more than one baby in a single pregnancy are at a greater risk of preeclampsia
• Women who are obese or have had other conditions such as kidney disease, diabetes or high blood pressure since before pregnancy are at an increased risk
• An imbalance between the blood coagulants prostacyclin and thromboxane
• Other factors include pollution, exposure to harmful chemicals and vitamin deficiencies