Is there a place for biochemical embryonic preimplantational screening?

The advent of assisted reproductive techniques such as intracytoplasmic sperm injection has markedly reduced the problem of unsuccessful fertilization in modern IVF. However, pregnancy rates and 'take-home-baby' rates remain unsatisfactorily low. Attempts to overcome low pregnancy rates by transferring a larger number of embryos to the mother often result in multiple pregnancies. The preimplantation embryo synthesizes several proteins that may signal its presence to the maternal system, and the interaction between the embryo and the endometrium is controlled, at least in part, by cytokines and growth factors. However, little is known about the interactions between the embryonic and maternal proteins. A better understanding of normal preimplantation embryo development may lead to improved in vitro culture conditions and higher pregnancy rates. This review gives an overview of the current knowledge of the embryonic factors produced during the preimplantation period. The development of the interleukin 1 system for screening human preimplantation embryos is also discussed. Current biochemical embryonic screening procedures are highly experimental, but increasing knowledge of the physiology of embryonic development might enable these screening procedures to be used to identify embryos that are capable of successful implantation.