The importance of glucose in culture media on fertilization and embryo development is still controversial. Although it has been reported that glucose is essential for fertilization process and biosynthesis of membrane lipid and nucleic acids, comparatively high levels of glucose in culture media may cause developmental arrest of cleavage stage embryos. The aim of this retrospective study is to examine whether exposure of sibling oocytes to different concentrations of glucose in culture media has any further effect on IVF outcome.

This retrospective study will include data from either standard IVF or Intracytoplasmic Sperm Injection (ICSI) cycles, in which sibling oocytes were equally divided and incubated separately in one of the following pairs of culture media:

1. Universal IVF medium vs. ISM1 medium ( Origio, Medi-Cult)
2. P1 medium vs. ECM medium (Irvine).

Fertilization rate,as well as embryo cleavage rate and morphology will be evaluated.

Inclusion Criteria:

• Sibling oocytes from cycles where at least 4 oocytes were retrieved

Exclusion Criteria:

• Less than 4 oocytes retrieved
• Partner has undergone testicular sperm extraction (TESE)

Sibling oocytes retrieved from women who have undergone IVF treatment in our IVF unit.