Prolonged Culture of Embryos
Usually, embryo transfer occurs on the second or third day after egg retrieval. With prolonged culturing of embryos (blastocyst culture), the development of the embryos can be monitored and the embryo that develops best can be chosen for the transfer.
Blastocyst transfer is typically used in cases where previous treatments have failed despite repeated attempts. Blastocyst culture facilitates embryo selection in cases where embryos cannot be frozen. In blastocyst culture, embryos are cultured in the laboratory for five or six days after egg retrieval. About one in three embryos develop into a blastocyst. If the culturing yields several good-quality blastocysts, they can be frozen for embryo transfer at a later date.