Improved embryo culture conditions have made extended culture to blastocyst stage increasingly popular. The choice between day 5 and day 6 is usually made on the blastocyst expansion. There is currently no data showing the impact of the day 6 transfer on ICSI outcomes when the choice of transfer day is made out according to the laboratory schedule. Indeed, some IVF centers minimize biological activity on weekends. In addition, work on weekends is the subject of recovery days that reduce the staff available on other week days. Is it possible not to schedule embryo transfers on Sundays without compromising ICSI outcomes? Retrospective cohort follow up study of ICSI cycles with blastocysts transfers on either day 5 or day 6, between January and December 2019 in a single center. The day 5 group comprised 416 cycles, and the day 6 group comprised 91 cycles. ICSI planned on Tuesday, with biological decision of an extended culture (EC) were programmed straight away for a day 6 transfer to avoid Sunday, without taking into account blastocyst expansion on day 5. ICSI planned on other days of the week with EC decision were scheduled for a transfer on day 5. The day 5 group comprised 416 cycles, and the day 6 group comprised 91 cycles. Our results indicate that the two groups were comparable respectively in terms of the mean age of patients (35.05 ± 5.01 VS 34.49 ± 4.46; p>0.05), the mean number of collected oocytes (11.11 VS 10.66; p>0.05); the oocyte maturity rate (63.35% VS 63.48%; p>0.05) and the mean number of blastocysts transferred (1.9 VS 1.78;p>0.05).Sperm parameters were also comparable between the two groups. The clinical pregnancy rate was higher in Day 5 group compared to Day 6 group, but this difference wasn't statistically significant (36,5 % VS 35,1 % ; p=0,91). Miscarriage rate wasn't statistically significant between the two groups (p> 0.05). There was also no difference in live birth rate (26,9 % VS 28,57% , p=0,8). When only singletons births were analysed, there was no difference in mean birthweight (2860g ± 540g VS 2690g ± 480g; p> 0,05). Furthermore, statistical significance was achieved when comparing male sex rate ( 40,2% VS 73,7%; p=0,03). The results did not change after controlling for possible confounding factors. Avoiding embryo transfers on Sundays may be possible without affecting ICSI outcomes