Influence of different oocyte insemination techniques on early and late morphokinetic parameters: retrospective analysis of 500 time-lapse monitored blastocysts.

OBJECTIVE: To determine how standard IVF vs. intracytoplasmic sperm injection (ICSI) fertilization influences early and late morphokinetic parameters during prolonged embryo culture.

DESIGN: Five-hundred expanded blastocysts that were monitored in a time-lapse monitoring incubator were analysed retrospectively. Early (pronuclear fading [PNf], t2-t9) and late (start of blastulation, expanded blastocyst) morphokinetic variables were scored according to published consensus criteria.

SETTING: Private infertility clinic.

PATIENT(S): A total of 209 consecutive infertile patients (mean ± SD age, 38.4 ± 4 years; range, 28-47 years) undergoing 238 natural IVF/minimal ovarian stimulation cycles during 2012-2014.

INTERVENTION(S): Minimal ovarian stimulation, oocyte retrieval, fertilization with standard IVF or ICSI, prolonged embryo culture in a time-lapse monitoring incubator.

MAIN OUTCOME MEASURE(S): Differences in morphokinetic parameters according to insemination techniques.

RESULT(S): In total, 29% and 71% of the whole cohort was fertilized with standard IVF and ICSI, respectively. During early cleavage stages (PNf to t4) there was a statistically significant delay (+1.5 to +1.1 hours) among IVF-fertilized embryos. By contrast, at the expanded blastocyst stage IVF-fertilized embryos showed faster development (-3.3 to -4.1 hours). After normalizing to the time point of PNf, differences in cleavage-stage parameters disappeared, but those at all blastocyst stages increased even further in favor of IVF-fertilized embryos (-3.2 to -5.7 hours).

CONCLUSION(S): The observed 1.5-hour time difference between standard IVF- and ICSI-fertilized embryos is an artificial phenomenon. At the blastocyst stages, however, genuine timing differences arise between IVF- and ICSI-fertilized embryos, possibly related to their different quality. Normalization to a common time point permits the joint analysis of IVF- and ICSI-fertilized embryos, thus increasing the size of studied cohorts.