Embryonic development in vitro is compromised by the ICSI procedure

The implantation rates achieved with intracytoplasmic sperm injection (ICSI ) are equivalent to those with conventional in-vitro fertilization (IVF) bu t information on embryonic development in vitro after ICSI is scant, In thi s paper we compare blastocyst formation after IVF and ICSI; we have also in vestigated the effect of the ICSI procedure with internal control of extrin sic (including paternal) factors. The first series comprised cases of IVF t reatment (il 101) for tubal infertility and ICSI (n = 96) for male infertil ity. The proportions of embryos developing to the blastocyst stage was sign ificantly lower after ICSI (8.9%, P < 0.001) than after conventional IVF (2 3.5%). In order to investigate the effect of the ICSI procedure in isolatio n, blastocyst formation was analysed in a second series of eight cases, in which sibling oocytes were non-selectively subjected to ICSI (n = 78) or IV F (n = 67) with spermatozoa from the same semen sample. It was found that 2 0% of ICSI embryos and 50% of IVF embryos formed blastocysts (P < 0.01), de monstrating that the ICSI procedure contributes to a reduced capacity for b lastocyst formation in vitro.