Reducing the Trigger Dose of Human Chorionic Gonadotrophin Does Not Affect Final Oocyte Maturation and Subsequently Pregnancy Outcome of Frozen-thawed Embryo Transfer

ObjectiveTo compare the efficacy of human chorionic gonadotrophin (hCG) at reduced doses of 2 000 IU and 3 000 IU for moderate or high responders with the dose of 5 000 IU in term of inducing final oocyte maturation for IVF/ICSI and the subsequent pregnancy outcome in frozen-thawed embryo transfer (FET).MethodsIn the retrospective cohort study, 2 166 patients undergoing IVF/ICSI with moderate or high response were recruited and classified into three groups according to the trigger dose of hCG: 2 000 IU (group A, n=722), 3 000 IU (group B, n=722) and 5 000 IU (group C, n=722). The main outcome was the proportion of mature oocytes retrieved, fertilization rates, clinical pregnancy rates, cumulative pregnancy rates and incidence of ovarian hyperstimulation syndrome (OHSS).ResultsNo evidence of statistically difference was found in the proportion of mature oocytes retrieved (89.92%, 91.40%, 90.20%, respectively) and fertilization rate (79.8%, 80.07%, 80.51%, respectively) among groups A, B and C. Serum E2 level on the day of hCG injection, the number of mature oocytes retrieved and good-quality embryos in group A were significantly higher than those in group B and group C. Clinical pregnancy rates per transfer cycle (45.95%, 43.97% and 44.25%), ongoing pregnancy rates (43.17%, 40.91% and 42.53%), implantation rates (30.74%, 27.78% and 29.86%) and cumulative pregnancy rates per patient (58.31%, 53.6% and 54.85%) were comparable among groups A, B and C. The incidence of OHSS in groups A, B and C (0%, 0.14% and 0.28%) was low, with no significant difference.ConclusionA reduced hCG dose of 2 000 IU for moderate or high responders leads to similar efficacy compared with a dose of 5 000 IU in inducing oocyte maturation without adversely affecting the pregnancy outcome meanwhile eliminating the risk of OHSS.