Pre-eclampsia was once blamed on toxins; the placenta is the real suspect
Doctors used to call pre-eclampsia toxaemia of pregnancy, believing poisons caused it. That idea was wrong. The strongest evidence now points to a placenta that implants abnormally, starving itself of blood and releasing substances that damage the mother's blood vessel linings. The condition affects 2 to 8 percent of pregnancies worldwide.
Pre-eclampsia is a pregnancy-specific disorder defined by newly raised blood pressure after 20 weeks, together with protein in the urine or signs of damage to organs such as the liver or kidneys. High blood pressure here means above 140 systolic or 90 diastolic on two readings more than four hours apart. Hippocrates described the related condition in the 5th century BC, and eclampsia, the stage marked by seizures, takes its name from a Greek word for a sudden, violent onset.
The leading explanation begins with implantation. If the placenta's cells fail to remodel the spiral arteries of the uterus properly, blood flow is poor, the tissue becomes short of oxygen, and it releases anti-angiogenic proteins and inflammatory signals into the mother's circulation. The result is widespread dysfunction of the endothelium, the inner lining of blood vessels, which drives the high blood pressure and other complications. One suggested root is incomplete immune tolerance of the placenta.
Genes play a part on both sides of the family. A 2005 study found women whose first-degree relative had an affected pregnancy were twice as likely to develop it, and men related to such cases also had a higher chance of fathering one. A key fetal gene, FLT1 on chromosome 13, can produce a soluble form called sFLT1 that suppresses vessel growth; pregnancies with an extra copy of chromosome 13 overproduce it and carry higher risk. Maternal and paternal genes have been implicated too.
Many signs are unreliable on their own. Swelling was once treated as a hallmark but is common in normal pregnancy, and upper abdominal pain can be mistaken for heartburn, so diagnosis rests on several features occurring together, confirmed when they fade after birth. Delivering the baby and placenta ends the process, though recovery can take days or weeks. Hypertensive disorders of pregnancy, including this one, caused 46,900 deaths in 2015, and affected women face higher risks of heart disease and stroke later in life.
Source: Pre-eclampsia
