The pathophysiology and the causes of preeclampsia are poorly understood. We still do not know what causes it in a pregnant woman.
Preeclampsia is defined as new onset of hypertension and proteinuria after 20 weeks of gestation in a previously non-hypertension and healthy woman. However, though rare, it is seen to occur before 20 weeks of gestation and even during the postpartum period.
Preeclampsia was, therefore, once called “the disease of theories,” but the advancement of research in the past ten years has yielded breakthroughs that may help us improve the diagnosis and even prediction, and lead to proper prevention and definite treatments. It also reduces the risk of maternal complications and effects on the fetus.
Formerly, it was believed to be due to a toxin and that is why preeclampsia was earlier called toxemia. But, that theory has been disproved. It was also referred to as pregnancy-induced hypertension.
Another reference for high blood pressure during pregnancy after 20 weeks is gestational hypertension. It differs from preeclampsia in that there is no protein present in the urine, which is a proven sign of this condition.
Possible causes of preeclampsia
Whether mild or severe, the known causes of preeclampsia remain unknown. A number of maternal, paternal, and fetal factors have been blamed for its development. But, we still have not been able to pin down the reasons that cause the symptoms.
Abnormal placental placement
Abnormal placental placement of the uterus leads to insufficient placental blood flow, ischemia, and widespread maternal endothelial dysfunction. This is considered the most speculated likely cause of preeclampsia.
Scientists speculate that the narrowing of the blood vessels of the placenta causes a problem with the development of the placenta due to restricted blood flow. This causes the restricted growth of the fetus.
Why the blood vessels develop differently is not known, but the following factors are suspected to be responsible:
- damage to the blood vessels
- reduced blood flow to the uterus
- some problems with the immune system
- genetic reasons
Genetic causes of preeclampsia
Research is underway to study whether the variations that take place in genes concerned with fluid balance, vascular endothelium function or development of the placenta play a role in the development of preeclampsia or its severity.
Environmental pollution can predispose to preeclampsia
An Australian study concluded that pregnant women with high exposure to traffic air pollution during their period of pregnancy were at an increased risk of developing this pregnancy complication.
Nutritional deficiency can cause preeclampsia
A deficiency of minerals such as copper, zinc, magnesium, and selenium can cause a functional deficiency of vitamin B. Ensuring a normal copper/zinc balance can help prevent this pregnancy condition.
Maternal immunology and autoimmune disorders
Immunological disorders in the mother such as Antiphospholipid syndrome (APS) are another speculated cause that can lead to preeclampsia. According to BMJ, APS increases the relative risk of pre-eclampsia by almost nine times.
Causes of early preeclampsia before 20 weeks
The development of preeclampsia before 20 weeks of gestation is rare. It can occur before 20 weeks of gestation and in the presence of a new onset of hypertension and proteinuria, it should always be considered in the differential diagnosis in pregnant women.
Though the causes of early preeclampsia are poorly understood, its early onset before 20 weeks is associated with a molar pregnancy, triploidy, Cushing syndrome, and antiphospholipid syndrome.
Causes of preeclampsia after delivery
Similarly, why preeclampsia sets in after childbirth is not known. However, it is believed that postpartum preeclampsia develops during pregnancy but shows its signs and symptoms after delivery. Postpartum eclampsia is very rare and though the baby is not endangered, 80% of the women die postpartum.