Preeclampsia · Visual journey
After week 20 of pregnancy, blood pressure rises and organs such as the kidneys or liver come under strain, often without symptoms. It all seems to start in the placenta.
Spiral arteryCarries the mother’s blood to the placentaOrgan
The baby’s blood runs through tiny branches called villi. The mother’s blood flows in from the spiral arteries and bathes them. Oxygen passes across, but the two never mix.
Tissue
In a healthy pregnancy, the placenta strips this artery of its muscle and widens it. In many cases of preeclampsia, especially those that start early, the placenta falls short.
The baby’s capillaryIts red blood cells pick up oxygen from the motherVillus
The baby’s blood is on the inside; the mother’s is on the outside. Between them, a very thin layer of cells lets oxygen and nutrients through.
Under the microscope
On the left is an infarct: an area of placenta that died because it didn’t get enough blood. The H&E stain colors the nucleus (the cell’s control center) purple and everything else pink.
Learn to read the slideA closer look at the artery
Pick a pregnancy and look at the muscle in the artery wall.
Healthy pregnancy
Preeclampsia
Healthy pregnancy. Cells from the placenta (the trophoblast) replace the muscle in the artery wall with fibrinoid material. The artery is left wide open, and plenty of blood gets through.
Preeclampsia. The trophoblast doesn’t push far enough into the wall, so the muscle stays and the artery remains narrow. Blood arrives in bursts, and the placenta runs short of oxygen over and over again.
Under the microscope
First, healthy tissue
On the left, the infarct: pale and crowded, with no blood and almost no nuclei. On the right, placenta with blood flow: purple nuclei and red blood.
On the left, the villi keep their shape but have lost their nuclei: their cells have died. On the right, the purple dots are still there.
From the placenta to the mother’s whole body
The infarct isn’t what raises blood pressure. It’s the mark left behind by poor blood flow. A placenta with poor blood flow releases substances that disrupt the mother’s blood vessels, especially in preeclampsia that starts early. The exact cause is still unknown.
That’s why urine is also tested for protein: it’s a sign the kidneys are struggling.
Hemolysis (red blood cells breaking apart), elevated liver enzymes and low platelets. Sometimes it’s the first sign, even without high blood pressure or protein in the urine.
What you can control
There’s no sure way to prevent it, and you often can’t feel it. What changes the outcome is finding it in time.
What you can do
Checking your blood pressure and testing your urine and blood can find it, even when you feel fine.
Preeclampsia can show up as late as six weeks after delivery, even with no warning signs beforehand. Delivering the placenta is the definitive treatment, but recovery takes days or weeks.
For people at high risk (preeclampsia in a past pregnancy, high blood pressure or diabetes before pregnancy, kidney or autoimmune disease, or twins), a low dose after week 12. Don’t start it on your own.
It raises your risk of high blood pressure and heart disease. Get your blood pressure checked regularly.
It depends on how far along you are, how severe it is and how the baby is doing.
I’m your friend, Dr. Carlo De la Sancha. Health and science for everyone.
What does a placenta with infarcts look like?
Watch the video “This placenta has infarcts” In the diagrams, the original English labels and their leader lines were erased or cropped out, and the white background was made transparent; none of the anatomy was redrawn. The opening microscope image is a version of the cited micrograph with more depth and contrast. The images in the comparison were only cropped and adjusted for brightness, contrast or sharpness.
Educational content for the general public. It doesn’t diagnose preeclampsia or replace a visit with your health care team: diagnosis and decisions depend on your blood pressure, your test results and your team’s evaluation.
