Enhancement of outcome from intracytoplasmic sperm injection: does co-culture or assisted hatching improve implantation rates?

In two separate prospectively randomized trials, intracytoplasmic sperm injection (ICSI) cycles were studied in a controlled manner to monitor the effects of either bovine oviductal epithelial cell co-culture (n = 119) or assisted hatching by zona drilling (n = 100). In the first study, immediately following ICSI, all eggs were placed directly either onto partial monolayers of bovine oviductal cells or into regular culture medium. Although the embryo developmental rate was apparently compromised in part by the presence of the co-culture cells, ultimately there were no significant differences in either the viable pregnancy rate (31.6% co-culture versus 29.0% control) or the embryonic implantation rate (11.4% co-culture versus 13.6% control). Assisted hatching also had no significant impact on ICSI cycle outcome in terms of either the viable pregnancy rate (30.0% assisted hatching versus 32.0% control) or the embryonic implantation rate (8.5% assisted hatching versus 13.5% control). However, in female patients aged > or = 35 years, assisted hatching appeared to convey a marginally significant benefit in terms of both the viable pregnancy rate (35.5% assisted hatching versus 11.1% control) and the embryonic implantation rate (10.3% assisted hatching versus 3.1% control). It seems that the overall improvement of ICSI cycle outcome cannot be achieved by the general application of either co-culture or assisted hatching. Nevertheless, it is possible that there remain specific patient groups that might benefit from selected use of either of these modalities.