It is completely normal for a pregnant woman to experience growth throughout her body. The feet are no different. In fact, the vast majority of pregnant women notice their feet swelling. There is also a very scientific reason for this phenomenon.
Pregnant women have swollen feet because their bodies retain so much fluid. Additionally, the fluid accumulates at the bottom of the body (the feet and ankles) thanks to gravity.
You need not worry too much about retaining so much fluid. Post-pregnancy, you should be able to fit back into all of those lovely shoes you can’t fit into anymore.