Developmental potential of slow-developing embryos: day-5 morulae compared with day-5 cavitating morulae

Area of Science:

• Reproductive Medicine
• Embryology
• In Vitro Fertilization (IVF)

Background:

• Embryo development and transfer timing are critical in IVF.
• Distinguishing between morulae and cavitating morulae (CAVM) on day 5 can impact outcomes.
• Understanding the developmental potential of slow-developing embryos is essential for optimizing IVF protocols.

Purpose of the Study:

• To compare ongoing pregnancy rates between day 5 morulae and CAVM transfers.
• To evaluate blastulation rates of day 5 morulae versus CAVM.
• To assess pregnancy rates of slow-developing blastocysts from these stages in frozen embryo transfer (FET) cycles.

Main Methods:

• Retrospective cohort study at a single tertiary care center.
• Analysis of 3,321 cycles involving 10,304 day 5 embryos cultured to day 6.
• Comparison of fresh embryo transfers, blastulation rates, and FET cycles involving embryos from morula and CAVM stages.

Main Results:

• Fresh embryo transfers showed comparable pregnancy (15.8% vs. 21.1%) and ongoing pregnancy rates (15.8% vs. 17.3%) for morulae and CAVM.
• Blastulation rate was significantly higher for CAVM (39.2%) compared to morulae (20.4%).
• Clinical pregnancy rates in FET cycles were similar for blastocysts derived from morulae (21.3%) and CAVM (24.7%).

Conclusions:

• Fresh transfer of day 5 morulae and CAVM yields comparable pregnancy outcomes.
• CAVM exhibits a superior blastulation rate compared to morulae.
• Transferring fresh, slow-developing embryos may be advantageous over extended culture and cryopreservation.