Fresh and frozen embryo transfers are two types of procedures used in in vitro fertilization (IVF). Fresh embryo transfer involves the transfer of an embryo to the uterus within three to five days of retrieval. Frozen embryo transfer, on the other hand, involves freezing embryos for later use. The frozen embryos can be thawed and transferred weeks, months, or even years after retrieval and  fertilization. Frozen embryo transfer is often used when a patient wishes to preserve fertility due to age, cancer treatment, or other reasons. The success rates for fresh and frozen embryo transfers vary depending on factors such as age and cause of infertility.