- This retrospective study examined interactions between male factor infertility (MFI), fertilization method and pre-implantation embryo development in 536 couples undergoing in vitro fertilization (4,126 embryos)
- MFI, regardless of severity, had no effect on the earliest development of any embryo
- MFI was associated with fewer usable embryos but did not affect overall developmental time to the blastocyst stage
- Intracytoplasmic sperm injection was associated with extended time to the blastocyst stage
- Sperm characteristics that affect embryo development may not be the same as those assessed during a routine semen analysis
In some fertility centers, including the Fertility Center at Massachusetts General Hospital, time-lapse imaging (TLI) is used to track pre-implantation embryo development and help select the most viable embryos for transfer.
Clinical fellow Caitlin R. Sacha, MD, and fertility specialist Irene Souter, MD, of the Fertility Center and Reproductive Endocrinology Unit at Mass General, and colleagues recently used TLI to study interactions between male factor infertility (MFI), fertilization method and embryo development. In Human Reproduction, they report that regardless of severity, MFI does not appear to affect embryo development to the blastocyst stage.
The researchers retrospectively studied 536 couples who underwent in vitro fertilization at Mass General between September 2013 and September 2016. In a TLI-monitored incubator, 4,126 embryos were cultured to the blastocyte stage. 1,178 embryos were from couples with MFI. 317 women were fertilized with intracytoplasmic sperm injection (ICSI) and the others with conventional IVF.
The researchers assessed six cleavage stages:
- PI — from pronuclei fading time to first cytokinesis
- P2 — from 2 cells to 3 cells
- P3 — from 3 cells to 4 cells
- P4 — from 4 cells to 5 cells
- P5SB — from 5 cells to early blastulation
- PSB — the overall interval from pronuclei fading time to early blastulation
Early Embryo Development
MFI, regardless of severity, had no effect on duration of P1, P2, P3 or P4 in any embryo. This remained true in subanalyses of usable embryos and ICSI embryos.
Late Embryo Development
When controlling for maternal and paternal ages, anti-Müllerian hormone and fertilization method (conventional IVF vs. ICSI):
- Duration of P5SB and PSB were not significantly different in MFI embryos than in embryos from couples with other infertility diagnoses
- The severity of MFI did not affect the duration of PSB, either overall or in usable embryos
Couples with MFI produced a lower percentage of usable embryos than those with other diagnoses, suggesting MFI has a broad impact on embryo quality and transfer potential.
Fertilization Method and Embryo Development
ICSI embryos had a longer PSB, primarily due to the prolonged duration of P5SB. However, PSB was not prolonged in embryos that were eventually discarded.
Thus, a longer duration of P5SB is not due to the semen characteristics captured by the MFI diagnosis. Other signaling factors arising from fertilization itself, or aspects of sperm quality not captured in routine semen analysis, might affect late development in usable embryos.
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