Fertilization will utilize either routine IVF or ICSI, depending upon the etiology of infertility and the quality of sperm. With ICSI, only mature oocytes will be inseminated. Embryo evaluation will occur per the clinic's standard protocols. Embryo assessment on day 5 post-fertilization will dictate final eligibility for study enrollment. Consenting participants with 3 or more cryopreservation-quality blastocysts (2BB or higher, graded according to Gardner's criteria) will then be randomized to either fresh single embryo transfer (SET) (and cryopreservation of all good quality supernumerary blastocysts) or a single frozen embryo transfer (FET) delayed to the subsequent menstrual cycle following cryopreservation of all of the good quality blastocysts. All FET cycles will be performed under a standard endometrial preparation protocol involving vaginal estradiol administration for approximately 14 days. Luteal support in either fresh or FET cycles will be with vaginal micronized progesterone, 200 mg vaginally 2-3 times daily, starting the day following fresh ET, and 6 days prior to FET, once documented endometrial thickness of 8 mm or more is achieved. The best quality blastocyst will be transferred first. Should the best blastocyst not survive warming in the FET group, the second-best blastocyst will be used. All cryopreservation will be performed by vitrification. Luteal phase progesterone will continue until either 10 weeks gestation (in an ongoing pregnancy) or until a documented negative serum hCG level drawn 14 days after the date of embryo transfer.