The swelling (edema) in your legs/ankles during pregnancy is a result of fluid leaking out of your blood vessels (capillaries) and into the surrounding tissues.
"Pitting edema" is the term used by clinicians to describe the pitting or impression that is left after pressing your fingers into an area where there is swelling. The fluid is retained in the tissues until it can be sent to your kidneys and removed.
It is important to note that this article is not intended to address "abnormal" clinical circumstances which can contribute to swelling as this is a topic that requires far more discussion and a thorough understanding of an individual's underlying medical condition. Any swelling during pregnancy may be a concern during pregnancy, particularly if the swelling involves your hands and face and not just your ankles.
As for the most common swelling seen in one's ankles, it is most pronounced at the end of the day after being on your feet for many hours. This swelling will often leave a demarcation/indentation from your stockings and is the result of gravity.
If my comments raise a concern as to whether you have abnormal swelling, you must bring this to the attention of your health care provider who can help you determine if it is clinically significant.
The following are some simple suggestions to help manage ankle swelling which is unrelated to other medical problems such high blood pressure or kidney problems:
1.) Whenever possible, elevate your legs during the course of the day and most definitely at night. Every night you are reminded of the fluid you are retaining during the day and may not even be aware of this. Have you ever noticed how often you find yourself getting up to the bathroom (voiding) in the middle of the night? This is because the fluid in your legs is being mobilized back into your blood stream and eliminated through your kidneys. While you are lying down/sleeping, your legs are at the level of your heart and gravity is not working against you. Your circulation is also not obstructed when you lie down, unlike when you are sitting. These factors allow for the removal of extra fluid during the night. The amount of fluid in your legs can literally be pounds of fluid by the end of the day.
2.) Using compression stockings is another measure you can take to decrease swelling. Unlike arterial blood flow, venous blood flow is a low pressure system and is the reason the low pressure of compression stockings can make such a big difference. Make sure the compression stockings you use are checked out with your provider. In certain clinical circumstances (vascular conditions) they are actually measured and ordered by your doctor. Support hose should ideally be full length and not have any constrictive bands at the ankles or thighs. These bands block blood return and act like a tourniquet which can make the problem worse and can lead to more serious vascular problems (blot clots etc.).
Always address any concerns about swelling with your health care provider and discuss what the best treatment options are to serve your particular circumstances.
Douglas Penta MD