I have a lot of swelling. When should I be worried?
During pregnancy, our blood volume increases dramatically to support the growing baby and placenta. Our bodies are always trying to stay in balance, and thanks to a process called osmosis, fluid can easily move across the membranes of the blood vessels to achieve that balance. Fluid always flows from less salty to more salty. When the fluid levels go up in our blood, it can dilute and make it less salty compared to the tissues around it. Osmosis then pulls the fluid out of our blood into our tissues, leading to swelling. This is a totally normal and common process, and is made worse when it gets warm. Swelling of the feet and legs (even pitting!), and swelling of the fingers to the point of not being able to wear rings is common and normal thanks to this process.
Increasing our sodium and potassium intake can help reverse this process. Drinking an electrolyte drink like Gatorade, Pedialyte, or salty broth can help make our blood saltier than our tissues and pull that fluid back out into our blood stream where it can be processed and released by the kidneys. This kind of swelling has nothing to do with preeclampsia and is not a warning sign. Even if you had regular swelling at one point and later got preeclampsia, it does not mean the earlier swelling was a warning sign, just that the two things both happened.
Now for preeclampsia swelling. Preeclampsia starts with a poorly functioning placenta. When it starts to struggle, it releases a chemical-protein called sFlt1. This chemical binds with another protein called VEGF. Now this second protein is the repairman of the cardiovascular system. It floats around repairing the tiny holes that form in our blood vessels from regular wear and tear. But when sFlt1 shows up, it prevents VEGF from doing its job, and the holes get bigger and bigger.
This process explains almost all of the symptoms of PE. The blood vessels clamp down to try to close the holes, leading to higher pressure just like covering up the end of a garden hose. When the blood vessels in the brain leak, we get cerebral edema, or when the blood vessels in the lungs leak, we get pulmonary edema. When the holes form in your kidneys, protein leaks into your urine. But the key part in this explanation is that the holes allow fluid to leak out of the blood into the tissues, causing swelling. You can see that this is a completely different process, leaking instead of osmosis.
Now, we want to be clear: even this kind of swelling is not an official part of the diagnostic criteria for preeclampsia. Instead, it is considered a red flag "other" symptom that would cause doctors to take a closer look at other things that *are* part of the diagnostic criteria.
What counts as a red flag that should be checked out?
Swelling of the hands beyond not being able to wear rings,
swelling of the face and especially the eyelids and lips, and/or
swelling so much you gain more than 5lb (2kg) in a week.
If you notice these things, call your doctor. It may turn out to be just a really bad case of regular pregnancy swelling, or it may lead to discovering that you have preeclampsia.