Involvement of programmed cell death in preimplantation embryo demise

Fragmentation is frequently observed in animal and human embryosobtained via in-vitro fertilization (IVF), and is known to beassociated with decreased pregnancy rates and poor survivalfollowing cryopreservation. We postulate that embryo fragmentationis a consequence of activated programmed cell death (PCD) andsubsequent apoptosis and discuss evidence of morphological,histological and biochemical features compatible with the occurrenceof PCD in preimplantation embryos. If PCD is an underlying causeof the high incidence of the fragmentation seen in human pre-embryos,it remains to be determined whether this is reflective of thenatural incidence of lethal chromo somes in the human populationor due to the IVF procedure and culture conditions.