Birth Control Pills Before IVF - Question!

I was told I'm being put on birth control pills for 21 days before my IVF cycle starts in February to make sure I don't get my period before Feb 1.  I'm actually due to get my period on Feb 1st naturally.  I'm very regular too! Does anyone know if and why it's still necessary? My nurse said I would probably be okay but I still have to take it just to be safe.  I really want to ttc this month though, and the bc pills put a stop to that completely.  Any help is greatly appreciated!