EMBRYONIC HUMAN CHORIONIC-GONADOTROPIN SECRETION AND HATCHING - POOR CORRELATION WITH CLEAVAGE RATE AND MORPHOLOGICAL ASSESSMENT DURING PREIMPLANTATION DEVELOPMENT IN-VITRO

Of 593 bipronucleate eggs allowed to develop in vitro, 275 (46%) achie ved the blastocyst stage and beyond, 124 (21%) initiated hatching, but only 49 (8%) fully hatched. About half of the pre-embryos (48%) which developed to these more advanced stages were incapable of secreting s ignificant amounts (> 200 mu IU) of cumulative human chorionic gonadot rophin (HCG) up to day 14. HCG production does not appear to begin unt il the expanded stage and is independent of hatching. Assessing cleava ge rate through successive stages and morphological grades up to the 8 -cell stage had little bearing on the ability of a pre-embryo to hatch or secrete HCG. Progression through the stages of preimplantation dev elopment in vitro does not always appear to be accompanied by the nece ssary biochemical stages. If only 46% of pre-embryos with two pronucle i are capable of achieving the blastocyst stage, and of these only 52% are capable of secreting HCG, then it follows that only 24% of the or iginal bipronucleate pre-embryos in vitro can be considered anatomical ly and biochemically competent. However, this is only applicable for p re-embryos not transferred or frozen, and is thus subject to a selecti on bias. Inability to detect HCG in vitro is not conclusive proof that a pre-embryo is developmentally incompetent. Similarly, failure to ha tch in vitro may not be taken as definitive evidence that hatching wou ld have failed had fertilization and development been completed in viv o. Nevertheless, if pre-embryonic development in vitro is similar to t hat in vivo, this may be a contributory factor in the low pregnancy ra tes following in-vitro fertilization treatment.