Fertilization and early embryology: Controlled comparison of Earle's balanced salt solution with Ménézo B2 medium for human in-vitro fertilization performance

Abstract

In order to optimize the in-vitro fertilization (IVF) procedure and to avoid the batch-to-batch fluctuations of in-house culture medium, we investigated the use of a commercially available medium. In our human IVF programme, a controlled comparison was performed from July 1991 to February 1992 between in-house Earle's medium and commercially available Ménézo B₂ medium. The major difference between the two tested media is the additional presence of amino acids and water-soluble vitamins in Ménézo B₂ and the different origins of the protein source, i.e. bovine serum albumin (BSA) in Ménézo B₂ and human serum albumin (HSA) in Earle‘s medium. In the first, auto-controlled study, sibling oocytes cultured in Ménézo B₂ showed a significantly higher fertilization rate than those cultured in Earle’s medium: 58.1± 37.2% and 52.1±36.9% respectively. After further culture of the fertilized oocytes, there was no difference in the morphological characteristics of the embryos cultured in the different media, although the rate of development was different. In Ménézo B₂ medium, a higher proportion of the embryos had reached at least the 4-cell stage at transfer. In the second, randomized study, effects on the pregnancy and implantation rates of both media were analysed. In the group of oocytes cultured in B₂, more excellent or good-quality embryos were available for transfer at a more advanced stage of development. No significant difference in pregnancy rate was observed: 39.1% per transfer in Earle‘s medium versus 40.5% per transfer in Ménézo B₂. The implantation rate per embryo as well as the ongoing implantation rate per embryo did not differ between the two media: 21.0 and 15.0% respectively for Earle’s medium and 20.5 and 14.3% respectively for Ménézo B₂ medium.