Effect of endometrial thickness and transplantation time on the incidence of ectopic pregnancy in frozen thawed embryo transplantation

  Objective  To investigate the effect of the endometrial thickness and embryo transplantation (ET) time on the incidence of ectopic pregnancy in frozen thawed embryo transplantation.

  Methods  A prospective study of 11 681 frozen-thawed embryo transplantation cycles in the Reproductive Center of Northwest Women and Children′s Hospital was conducted to analyze the pregnancy outcomes, including 6 901 cycles of clinical pregnancy and 75 of ectopic pregnancy. According to the embryo transplantation time, the FET cycles were divided into D₃ embryo transplantation group (5 912 cycles in embryo period) and D₅ blastula transplantation group (5 949 cycles in blastula period). And were further subdivided into ≤9 mm group, >9~12 mm group and >12 mm group according to endometrial thickness. The incidence of ectopic pregnancy of varied groups were compared.

  Results  There were 45 cases with ectopic pregnancy in the D₃ embryo transplantation group, and 30 cases in D₅ blastocyst transplantation group, and its incidence of ectopic pregnancy showed a significant difference(P < 0.05). Compared with ≤9 mm group, the incidence of ectopic pregnancy in >9~12 mm group and >12 mm group were significantly lower.

  Conclusion  D₅ blastula transplantation group has significantly lower risk of ectopic pregnancy than D₃ embryo transplantation group, endometrial thickness can be independent factor of ectopic pregnancy.