The Pregnancy Outcomes of Day 2 versus Day 3 Embryo Transfer: A Cross-Sectional Study

Document Type : Original Article


1 Endocrinology and Female Infertility Department, Royan Institute

2 Obstetrics and Gynecology Department, Iran University of Medical Sciences

3 Epidemiology Department, Royan Institute


Background: The objective was to evaluate whether extending the embryo culture period from 2 to 3 days would yield a more optimal selection of viable embryos, thereby increasing the pregnancy rate.
Materials and Methods: We have retrospectively analyzed pregnancy rates in the patients who had embryo transfer either on day 2 (582 patients) or on day 3 (387 patients) post-insemination over a 10-month period. The relationship between the quality score of day 2 and day 3 embryos and their respective pregnancy rates was also analyzed.
Results: The demographic and clinical characteristics were similar in both groups. Embryos transferred on day 2 or day 3, were similar morphologically& we found no difference in the distribution of grades between patients who became pregnant and those who failed to become pregnant. Pregnancy rates were slightly higher in patients who had embryo transfer on day 3 (40.72%) than patients who had transferred on day 2 (38.96%), but this difference was not significant.
proportion of embryos with 2-3 cells, four cells, and 5-7 cells, which selected for transfer, showed significant difference between day 2 and day 3 (p<0.05). There was also significant difference between pregnant and non-pregnant women based on embryo cell numbers on day two (p<0.011).
Conclusion: Extending the embryo culture period from 2 to 3 days had no adverse effect on pregnancy rate. Embryo transfer could be done on days 2 or 3 according to the convenience of the patient and the medical team.