Laboratory techniques for handling gametes and embryos.

This review describes some basic and novel principles pertaining to the science of in vitro fertilization and embryo culture. Several systems for cell-free culture of gametes and embryos are described. The advantages of a coculture or helper cell system was investigated in several clinical trials using bovine cells from the reproductive tract. Improved embryonic morphology and implantation indicate that standard IVF culture provides suboptimal conditions. Microsurgical methods for assisting in vitro fertilization in cases of severe male factor infertility are also discussed. Thus far, it has been demonstrated that mechanical opening of the zona pellucida by methods such as partial zona dissection enhances fertilization. In addition, the introduction of a limited gap in the zona seems to facilitate hatching of the blastocyst, which may benefit all patients undergoing in vitro fertilization.