Fertilization and early embryology: Co-culture of human pronucleate oocytes with their cumulus cells

The aim of this prospective randomized work was to study the value of co-culturing human pronucleate oocytes with their cumulus cells. A total of 550 fertilized oocytes from 95 in-vitro fertilization patients were randomly divided into two groups on the day after insemination. Group A oocytes (n = 260) were left undisturbed with their attached cumulus cells and group B oocytes (n = 290) were dissected from their cumulus cells. Both groups were incubated and examined daily for 3 days. In group A, 78% (202/260) reached the 4-cell stage 48 h after retrieval compared to 69% (200/290) in group B. At 72 h after retrieval, 70% (141/202) had reached the 8-cell stage in group A compared to 56% (112/200) in group B. The percentages of grade 1 embryos at 48 and 72 h after retrieval were 70% (141/202) and 76% (107/141) in group A compared to 50% (100/200) and 43% (48/112) in group B respectively. We concluded that co-culture of human oocytes with their cumulus cells significantly decreased their fragmentation and increased the number of embryos that reached the 4-cell and 8-cell stages with regular blastomeres. The technique is simple and avoids the use of heterogeneous cells.