With standard IVF (I-V-F), eggs and sperm are combined in the laboratory to create human embryos. These are normally placed back into the womb after three days of growth. Blastocyst (BLASS-toe-syst) culture is a new technique where embryos are grown for five- to six days in the laboratory, two- to three days longer than standard IVF. This additional time for development helps select 'healthier' embryos, and may increase the chance to conceive. Since only one to two blastocysts are placed back into the womb, the chance for high order multiple pregnancy such as triplets or more is reduced. Embryos may also be frozen at the blastocyst stage and used in the future.
