OBJECTIVE: To measure fetal developmental potential of mouse eggs fertilized and cleaved in modified Ham's F-10 medium (Sigma Chemical Co., St. Louis, MO) containing the chelating agent, ethylenediaminetetraacetic acid (EDTA), as a model for establishing criteria for human IVF and GIFT procedures. DESIGN: Optimum concentrations of EDTA in modified Ham's F-10 were established by measuring blastocyst development of in vivo fertilized zygotes from a random bred (CD1) mouse strain. Postimplantation development of in vitro fertilized eggs from a hybrid inbred (B6D2F1) mouse strain was measured after conception in the modified Ham's F-10 medium without or with human serum or EDTA and compared with the results of in vivo fertilized eggs. Mouse embryo development potential and pregnancy rates (PRs) of recipients were compared with those calculated from theoretical probabilities. RESULTS: The addition of 10 to 100 microM EDTA to modified Ham's F-10 supported development of > 60% of the in vivo conceived zygotes to the blastocyst stage in the absence of serum; the addition of human serum significantly decreased embryo development to blastocysts (23%). Pregnancy rates (30% to 50%) of recipients of the in vitro conceived mouse embryos were similar for embryo cohorts from all culture conditions tested. The overall yield of fetuses from total embryos transferred was significantly higher for the groups developed in modified Ham's F-10 with 100 microM EDTA (37%) compared with embryos developed in modified Ham's F-10 alone (18%) or in modified Ham's F-10 with human serum (18%). CONCLUSIONS: [1] Based on fetal development in pregnant recipients, approximately two thirds of the mouse eggs fertilized in modified Ham's F-10 with 100 microM EDTA (or in vivo) had the potential to give rise to offspring. [2] Given the viability rate, the observed PRs of foster mothers receiving four to six embryos were only two thirds of the theoretically possible, suggesting the hormone and/or surgical interventions of the recipients reduced their pregnancy potential. [3] Including 100 microM EDTA during mouse conception in modified Ham's F-10 improved the fetal developmental potential to that of in vivo derived mouse embryos.