Blastocyst formation in in vitro fertilization versus intracytoplasmic sperm injection cycles: influence of the fertilization procedure.

OBJECTIVE: To compare the quality of early cleaving embryos and blastocysts obtained by IVF or intracytoplasmic sperm injection (ICSI).

DESIGN: Retrospective study.

SETTING: Tertiary infertility center.

PATIENT(S): Sibling oocytes of 104 patients in 104 IVF vs. ICSI cycles.

INTERVENTION(S): Cumulus oocyte complexes (n = 1,358) were randomly subjected to ICSI or IVF.

MAIN OUTCOME MEASURE(S): Embryo development and blastocyst formation rate. The blastocyst quality and cycle efficiency were also evaluated.

RESULT(S): Early embryo cleavage was higher after ICSI (37.1%) compared to IVF (14.1%). The percentage of > or =4-cell embryos on day 2 and > or =8-cell embryos on day 3 was similar for both procedures. The overall blastocyst formation was not different between ICSI (50.2%) and IVF (54.8%), neither was the percentage of good-quality blastocysts (31.3% for ICSI and 36.0% for IVF). The total cycle efficiency (percentage of embryos transferred and frozen per two pronuclei [2PN]) was comparable for the two techniques (51.7% for ICSI and 57.4% for IVF).

CONCLUSION(S): No differences were found on sibling oocytes in the embryo development and blastocyst formation, irrespective of the fertilization procedure. Earlier suggestions that the ICSI technique may result in impaired blastocyst development were not confirmed in this study.