alifriqui on "Very basic question about egg retrieval"

Hi! I have a very general question about egg retrieval. I've been doing a lot of reading lately about the procedure and I'm stumped on something. I probably just have not read enough, but maybe someone here can explain it to me. When we are born, we are born with all the eggs we will ever have, right? So when someone goes in for their egg retrieval, how come so few are retrieved? If 20 or so eggs, for example, are retrieved, where are the rest? How come we are able to go through the retrieval process more than once? How would you get additional eggs a second (third, etc.) time if you only got those 20 the first time? I'm probably missing something very basic, so hopefully someone can explain it? Thank you!