The oocyte-to-baby rate of day 2, day 3 versus day 5 embryo transfer: a retrospective study

To investigate whether the time of embryo transfer (ET) affect the oocyte-to-baby rate.

The database was retrospectively analyzed including total number of oocytes collected and corresponding oocyte-to-live baby born (LBB) rate. Then the relationship between different time of embryo transfer and oocyte-to-baby rate was compared. In a year period all patients undergoing infertility treatment were included in the study. The outcome parameters were total number of oocytes collected and corresponding oocyte-to-LBB.

For patients under the age of 35 years, there was no increase in oocyte-to-LBB regardless of the time of ET. For patients older than 35 years, the oocyte use rate increased significantly when embryo was transferred on day 2. Oocyte-to-baby rates were also analyzed after grouping patients on the number of oocytes retrieved per cycle. For patients < 35 years, the oocyte- to -LBB rate increased significantly on day 3 if < ten oocytes were obtained. whereas for patients > 35 years, the oocyte-to-baby rate was best on day 2 when about 15 oocytes were retrieved.

This retrospective analysis demonstrated the relationship between the time of ET and ooctye-to-baby rate that is indicative of a more biologically efficient reproductive system.