Abstract: To investigate the influence of duration of gonadotropin (Gn) administration on the clinical outcome of in vitro fertilization embryo transfer (IVF-ET). Methods: A total of 3 221 cycles of short protocol or antagonist protocol in our center from January 2012 to December 2012 were included in the retrospective study. According to the different duration of Gn administration, all patients were divided into group A (≤7 days, n=58) and group B (＞7 days, n=3 163). The different clinical parameters, such as age, duration of infertility, body mass index (BMI), basis estradiol (E ₂), folliclestimulating hormone (FSH), the number of antral follicle, the number of oocytes, endometrium thickness, fertility rate, good quality embryo rate, impatation rate and clinical pregnancy rate were compared between the two groups．Results: There was no significant difference in age, duration of infertility, BMI, basis E ₂, FSH, the number of antral follicle between the two groups. The number of oocytes in group A was fewer than that in group B ［（8.2±5.6）vs.（12.1±8.3），P=0.009］; endometrium thickness on the day of HCG in group A was thinner than that in group B ［（9.9±2.1） mm vs.（10.4±1.6） mm，P=0.002］. There was no significant difference in fertility rate, good quality embryo rate, impatation rate and clinical pregnancy rate (36.2% vs. 33.6%, P> 0.05). There was no significant difference in clinical pregnancy rate between the two groups in short protocol (33.3% vs. 27.2%, P> 0.05). In the same way, there was no significant difference in clinical pregnancy rate between the two groups in antagonist protocol (37.5% vs. 36.6%, P> 0.05). Conclusion: Although short duration of gonadotropin administration in short protocol and antagonist protocol has association with fewer number of oocytes, it may not affect the outcome of IVF- ET.

Key words: Gonadotropins, Fertilization in vitro, Embryo transfer, Pregnancy rate