Can't speak for anyone else, but this was my protocol.
Birth control for at least 2 weeks
Ultrasound & blood test to make sure everything looks good & quiet.
Off bc pills for a few days before starting estrogen.
Back in a week for ultrasound & check estrogen.
Back in a week for ultrasound & check estrogen & progesterone. Start progesterone & methylprednisone & baby asprin.
6 days later, FET. Continue w/ estrogen, progesterone & baby asprin until beta.