Publication:

Stage matters: comparing day 4 versus day 5 versus day 3 frozen embryo transfers

Background Morphological grading of embryo transfer remains as key determinant for in vitro fertilization (IVF) success. Though day 5 embryo transfer has more implantation potential, day-4 transfer is considered in cases where we suspect a risk of “no embryo to transfer.” Aim was to compare the pregnancy outcomes of day-4 versus day 3 versus day-5 frozen embryo transfer.

Methods This is a retrospective comparative study. 672 sub-fertile women who underwent intracytoplasmic sperm injection (ICSI) during a period of 6 years (2019-2025) were included in the study. These women totally underwent 947 embryo transfers. Fresh embryo transfers were excluded from the study. Patients were followed up till delivery and their pregnancy outcomes were studied.

Results The clinical pregnancy rate of day 4 embryo transfer was not statistically significant when compared with day 3 and day 5 groups (p=0.13). The live birth rate and miscarriage rate in day 4 embryo transfers were comparable with other two groups and was approaching clinical significance (p=0.06). The preterm delivery rate was lower in day 4 group when compared to other two groups and was statistically significant (p=0.006). The number of ectopic pregnancies was also less in day 4 group when compared to others (only two in day 4 group, five in day 3 group and three ectopic pregnancy in day 5 group).

Conclusions In this study, day 4 embryo transfer gives comparable results when compared with blastocysts in terms of clinical pregnancy rate, reduced miscarriages, preterm deliveries and ectopic pregnancies.