Optimizing the culture environment in the IVF laboratory: impact of pH and buffer capacity on gamete and embryo quality

Supplying and maintaining appropriate culture conditions is critical to minimize stress imposed upon gametes and embryos and to optimize the in-vitro environment. One parameter that requires close scrutiny in this endeavour is pH. Though embryos have a limited ability to regulate their internal pH (pHi), oocytes lack robust mechanisms. Thus, careful attention to external pH (pHe) of culture media is imperative in IVF. Ability to withstand deviations in hydrogen ion concentration varies depending on culture conditions, as well as laboratory procedures. Cryopreserved–thaw–thawed embryos, as well as denuded oocytes, are especially susceptible to perturbations in pHe. Therefore, proper setting, monitoring and stabilizing of pHe during IVF laboratory procedures is a crucial component of a rigorous quality control programme. Here, importance of both pHi and pHe in respect to gamete and embryo quality are discussed. Furthermore, factors influencing selection of pHe, as well as emerging methods to stabilize pHe in the IVF laboratory are detailed.