ABSENCE OF HEAT-TREATMENT OF SERUM FOR CULTURE-MEDIUM SUPPLEMENTATION DOES NOT ADVERSELY AFFECT THE OUTCOME OF IN-VITRO FERTILIZATION

This study was carried out to determine if not heat-treating serum prior to use for medium supplementation adversely affected in-vitro fertilization (IVF) of human oocytes. Morphologically mature human oocytes derived from 135 patients undergoing IVF treatment were studied. A total of 504 oocytes were incubated, inseminated and the resulting pronuclear oocytes cultured further in Earle's balanced salt solution (EBSS) supplemented with 10% non-heat-treated serum. Comparisons of fertilization rate and embryonic development were made between these and 687 control oocytes derived from the same patients but incubated, inseminated and resulting pronuclear oocytes cultured further in EBSS supplemented with 10% heat-treated serum. The fertilization rate of 74.4% (375/504) of oocytes handled in serum-supplemented medium that had not been heat-treated was significantly better than the rate of 67.7% (465/687) for controls (P < 0.0125). The proportion of pronucleate oocytes that cleaved was also significantly better in the non-heat-treated serum group: 270/300 (90%) versus 307/375 (81.8%) (P < 0.0025). There was no significant difference in the proportion of embryos with four or more cells at the time of embryo transfer. The results show that the absence of heat treatment of serum used to supplement culture medium has no adverse effect on the fertilization rate and short-term embryo development in vitro; hence we suggest that serum heat treatment is an unnecessary procedure and could be abandoned.