us girls are born with all our eggs. as apose to males who produce sperm as they use it. so when you are born you have millions of eggs already in your overies. i read somewhere that this reserve is aleady halved by time you reach puberty (might need to confirm that im on my phone so cant atm). some women it takes a while for their period to return after having a baby.
in fact im going to do some research and get back to you with proper facts ratger than trying to remember stuff i use to know.