Purpose: To compare embryo quality and outcomes of blastocysts thawed and transferred the same day with those thawed and cultured overnight before transfer.
Methods: In this retrospective study, patients with infertility who underwent thawed embryo transfer (TET) the same day as thawing (0TET group) and those that received TET after embryos were thawed and cultured overnight before transfer (1TET group) were enrolled. Univariable and multivariable logistic regression were performed to detect the factors associated with the clinical pregnancy rate (CPR), implantation rate, miscarriage rate, and multiple pregnancy rate.
Results: A total of 489 patients (489 cycles) were included with 234 in the 0TET group and 255 in the 1TET group. There were no significant differences between the two groups with respect to age, body mass index (BMI), basal FSH and estradiol (E2) level, and causes of infertility (all, p > 0.05). There were no significant differences in the CPR, implantation rate, miscarriage rate, or multiple pregnancy rate between the two groups (all, p > 0.05), and this finding was irrespective of the endometrial preparation method.
Conclusions: Pregnancy outcomes are the same for blastocysts thawed and cultured overnight 1 day before transfer and those thawed and transferred on the same day.
Keywords: Blastocyst culture; Embryo transfer; Freezing; In vitro fertilization; Vitrification.