After your lining check, one will typically continue their estrogen regimen and be instructed to add the progesterone medication in a few days. Progesterone helps the uterine lining receptivity to embryo implantation. Typically progesterone is started on days 11-13 from the beginning of the estrogen protocol and sets the actual embryo transfer procedure in motion and determines when your embryo(s) will be thawed and transferred.
Cleavage (Day 3) embryos will be transferred 4 days after the start of progesterone. Blastocyst (Day 5 . . . or 6/7) embryos will be transferred 6 days after the start of progesterone.