Protocol describes a method for removal of mouse ovaries in combination with the administration of progesterone, which causes the arrest of blastocyst development. This procedure is performed during the afternoon of the third day of pregnancy to ensure that the morulae have moved sufficiently into the oviducts and will be less likely to be damaged during the ovariectomy. - [Read Ovariectomy for Induction of Blastocyst Implantation Delay Protocol]