In procedures like in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), multiple viable embryos can be obtained at once. Typically, one embryo is transferred to the uterus, and any extra embryos are frozen for future use.
Frozen embryos can be stored safely for several years. In our laboratory over 95% of frozen embryos remain viable after thawing.
The transfer of frozen embryos usually takes place in a modified natural cycle, 5-6 days after ovulation. The uterine lining can also be prepared with hormone medication, especially when the patient has irregular cycles or if ovulation does not occur.