NEW YORK (Reuters Health) – Among women undergoing IVF and who respond poorly to ovarian stimulation, successful outcomes are not increased when embryo transfer takes place on day 2 rather than day 3 after fertilization, a group at Stanford University, California has shown.

Writing in a September 1st online issue of Fertility and Sterility, Dr. Lora K. Shahine and colleagues note that assisted reproduction is challenging in the 9% to 24% of women who have a poor response to controlled ovarian stimulation.

“Patients that respond poorly to ovarian stimulation (have few embryos available to transfer) have low success with IVF and limited treatment options.” Dr. Shahine explained via email. “One hypothesis is that these patients have fragile embryos that may do better (survive) in the uterus rather than in culture in an IVF lab. If this is true, then their chances of pregnancy may be improved with earlier return of the embryos to the uterus.”

To evaluate this strategy, the team identified 386 possible poor responders. Ultimately, 251 of them who had at least one fertilized oocyte were randomized to have all available embryos transferred on either day 2 or day 3.

The clinical pregnancy rate, the primary outcome, was 15.4% in the day 2 group and 16.4% in the day 3 group (p=0.8). “The timing of embryo transfer had no impact on pregnancy rates,” said Dr. Shahine.

Furthermore, the researchers could not identify any subgroup that benefitted from earlier transfer. “We did not find a difference in clinical pregnancy rate between treatment groups in patients analyzed by the following subgroups: female age >\=40 years versus \=12 mIU/ML versus lower CD3 FSH level, patients with only one embryo to transfer, patients with a history of two or more failed IVF cycles, patients with different ovarian stimulation protocols, or patients with or without intracytoplasmic sperm injection or assisted hatching,” the authors write.

Dr. Shahine and colleagues conclude that the choice of day 2 or 3 embryo transfer can be left to clinician and patient preferences.

Reference:

Day 2 versus day 3 embryo transfer in poor responders: a prospective randomized trial

Fertil Steril 2010.