Is there a place for biochemical embryonic preimplantational screening?

The advent of assisted reproductive techniques such as intracytoplasmic spe rm injection has markedly reduced the problem of unsuccessful fertilization in modem IVF. However pregnancy rates and 'take-home-baby' rates remain un satisfactorily low. Attempts to overcome low pregnancy rates by transferrin g a larger number of embryos to the mother often result in multiple pregnan cies. The preimplantation embryo synthesizes several proteins that may sign al its presence to the maternal system, and the interaction between the emb ryo and the endometrium is controlled, at least in part, by cytokines and g rowth factors. However, little is known about the interactions between the embryonic and maternal proteins. A better understanding of normal preimplan tation embryo development may lead to improved in vitro culture conditions and higher pregnancy rates. This review gives an overview of the current kn owledge of the embryonic factors produced during the preimplantation period . The development of the interleukin 1 system for screening human preimplan tation embryos is also discussed. Current biochemical embryonic screening p rocedures are highly experimental, but increasing knowledge of the physiolo gy of embryonic development might enable these screening procedures to be u sed to identify embryos that are capable of successful implantation.