What are the causes of your vagina to be swollen after intercourse?

Blood flow: In preparation for intercourse, part of arousal is the vagina having increased blood flow. All of the tissues in the area get swollen in preparation for intercourse. In addition, the act of intercourse can cause some trauma (albeit pleasurable) to the tissues causing inflammation. The combination of these plus many other things results in some swelling. It will resolve after a few hours.