For IVF patients with only one embryo, what is the best transfer day?

This study looked at whether embryo transfer on day 3 or day 4 to 5 was better for patients undergoing IVF (in vitro fertilization). This study found that day 3 transfer led to better outcomes compared to transfer on a later day.

In vitro fertilization (IVF) is an infertility treatment in which eggs are removed from a woman, fertilized, and introduced to the womb. One cause of unsuccessful pregnancy after IVF is if the embryo does not implant in the uterus. Traditionally, embryos were transferred three days after fertilization.

However, improvements in culture methods have allowed embryos to be grown until days 4 to 6. Embryos that survive for 4 to 6 days are more likely to lead to successful pregnancies. However, choosing the highest-quality embryos is challenging when there is only one embryo. It is not clear which day of embryo transfer is best for patients with a single viable embryo.

This study used records of 1384 patients undergoing IVF. Only one cycle per patient was included in the study. All patients had a single viable embryo on day 3. 1017 patients had a day 3 transfer (Group A). 367 patients had a day 4 to 6 transfer (Group B).

Significantly more embryos in Group A were of high quality compared to Group B (59.3% vs 32.2%).  Significantly more patients in Group A had a positive pregnancy test compared to Group B (16.7% vs 9.5%). Day 3 transfer was significantly associated with a 2.60-fold higher chance of a positive pregnancy test.

Significantly more patients in Group A had a confirmed pregnancy (via ultrasound) compared to Group B (14.7% vs. 6.8%). Day 3 transfer was significantly associated with a significant 3.71-fold higher chance of a confirmed pregnancy via ultrasound.

Lastly, significantly more patients in Group A had a live birth (9.7% vs. 4.4%). Day 3 transfer was significantly associated with a significant 4.08-fold higher chance of a live birth.

This study found that for IVF patients with a single viable embryo, day 3 transfer led to better outcomes than day 4 to 6 transfer. The authors suggest that the uterus may be a better environment for early embryos than tissue culture.

This study looked back in time to analyze data. More studies are needed to confirm these results. Also, it is unclear if pregnancy rates would be higher with day 3 transfers in patients with more than one embryo.

Discuss your options for the day of embryo transfer with your doctor.