Effect of age and embryo number transferred on outcomes of frozen-thawed cycles

Objective To investigate the effect of age and embryo number transferred on clinical pregnancy rate,implantation rate and multiple pregnancy rates of frozen-thawed cycles (FET).Methods We retrieved 1251 patients underwent FET cycles from January 2010 to May 2012.These cycles were divided into 4 groups according female age:group A,＜ 30 years old,n =549 ; group B,30-34 years old,n =433; group C,35-38 years old,n =168; group D,≥39 years old,n =101.The clinical pregnancy rate,implantation rate and multiple pregnancy rate with 2 or 3 embryos transferred of each group were analyzed.Results The clinical pregnancy rate and implantation rate were decreased significantly with age of patients (P ＜ 0.05),but there was no significant difference in multiple pregnancy rates (P ＞ 0.05).The differences of clinical pregnancy rate,implantation rate with 2 or 3 embryos transferred in group A,B and C were not significant (P ＞ 0.05).The clinical pregnancy rate with 3 embryo transferred was significantly higher than with 2 in group D (P ＜ 0.05).The multiple pregnancy rates with 2 embryos transferred was significantly lower than with 3 in group A,but there was no significant difference in multiple pregnancy rate with 2 and 3 of group B,C and D.Conclusions In frozen-thawed embryo transfer cycles,ideal clinical pregnancy rate could be received from patients with age ≤38 years old and 2 embryos transferred; and for patients aged ≥39 years old,better pregnancy rate could be obtained when 3 embryos were transferred; it was inevitable that multiple pregnancy was got no matter 2 or 3 embryos were transferred. Key words: Embryo number transferred; Female age; Clinical pregnancy rate; Frozen-thawed embryo; Multiple pregnancies