The surplus human embryo: its potential for growth, blastulation, hatching, and human chorionic gonadotropin production in culture.

Early embryos that were unsuitable for transfer to patients or for cryopreservation were cultured either in a human tubal fluid (HTF) or a minimum essential medium (MEM). A significantly higher proportion of embryos developed to blastocysts in MEM (26.8%) than in HTF (14.5%). Approximately similar proportions of embryos formed blastocysts in MEM in the presence or absence of serum. The rate of embryo growth to blastocysts was similar in all media. Blastocyst hatching occurred in MEM + or - serum, but it failed to occur in HTF with serum. Released human chorionic gonadotropin (hCG) from hatched and intrazonal blastocysts was detected by day 8 after fertilization. The mean amount of hCG produced by day 14 was 19,500 mIU from hatched and 1,550 mIU from intrazonal blastocysts. Serum stimulated the output of hCG.