Differential pH in embryo culture.

OBJECTIVE: To determine the optimum pH in sequential media for embryo culture around the fertilization-zygote stage and cleavage stage, with use of a mouse embryo assay.
DESIGN: Experimental laboratory study.
SETTING: University Hospital and University Research Unit. ANIMAL(S): F1 hybrids between CD1 female and BDF male mice. INTERVENTION(S): Fertilized, one-cell mouse embryos were cultured 5 days in test media where pH was changed at defined time intervals. MAIN OUTCOME MEASURE(S): Percentage of good-quality embryos, defined by strict morphology. RESULT(S): A significantly improved development was observed when pH was as high as 7.30 before the pronuclear stage and lowered to pH 7.15 during the cleavage period. CONCLUSION(S): Good embryo development is consistent with two different pH values in sequential culture media. This could have important implications for embryo culture in human IVF.