[Analysis of pregnancy outcome of single and double blastocysts in the freeze-thaw cycle].

Objective: To compare the clinical outcomes of one and two blastocysts in the freeze-thaw transplantation cycle. Methods: Totally 3 675 cycles of frozen thawed blastocyst transplantation in Reproductive Medical Center of the Second Nanning People's Hospital from January 2012 to December 2016 were analyzed retrospectively. According to the quantity and quality of transferred blastocysts, all the patient were divided into two groups: (1) one embryo group, including the single excellent group (one high quality blastocyst) and the single non excellent group (one non high quality blastocyst); (2) two embryo groups, including the double excellent group (two high quality blastocysts), the one excellent and one non excellent group (one high quality blastocyst+one non high quality blastocyst), and the two non excellent group (two non high quality blastocysts were transplanted). Then the patients were divided into subgroups according to their ages: less than 35 years old, 35-40 years old and over 40 years old. On this basis, the implantation rate, clinical pregnancy rate, multiple birth rate and live birth rate were compared. Results: (1) The implantation rate, clinical pregnancy rate, multiple birth rate, preterm birth rate and live birth rate were all significantly increased, while the abortion rate was significantly reduced in the double blastocyst group (all P 0.05), but the multiple birth rate and preterm birth rate were significantly increased (P 40 years old, there were no significant differences in clinical pregnancy rate and live birth rate between the two groups (P>0.05). There were no significant differences in implantation rate, clinical pregnancy rate and live birth rate between double non optimal group and single non optimal group (P>0.05). Conclusion: No matter the age of the patients, if the couple have high quality blastocysts, we should give priority to single high quality blastocyst transplantation; even if they have no high quality blastocysts, we should also consider single blastocyst transplantation, in order to reduce the risk of multiple pregnancy and improve the cumulative live birth rate, so as to improve the pregnancy outcome.