The effect of flexible low-dose GnRH antagonist on pregnancy outcome in the fresh embryo transfer cycle of IVF-ET: a randomized controlled trial

Objective To explore the practicality and effectiveness of a flexible low-dose protocol in the fresh embryo transfer cycle: reducing the total amount of antagonist by increasing the interval between administrations of Cetrotide. Methods A total of 211 patients with normal ovarian reserve who accepted GnRH-ant protocol for IVF-ET were selected, and they were randomized to the flexible low-dose antagonist group (test group, n = 101) or the conventional dose antagonist group (control group, n = 110). The initial dose of Cetrotide in the test group was 0.25 mg every other day, and then the dose was adjusted to 0.25 mg every day based on the subsequent luteinizing hormone (LH) levels. The dosage of Cetrotide in the control group was 0.25 mg per day. The primary outcome was the clinical pregnancy rate. Secondary outcomes included the incidence of premature LH rise, total dosage of Cetrotide, number of oocytes retrieved, number of fertilized oocytes, number of high-quality embryos, biochemical pregnancy rate and ongoing pregnancy rate. Results There was no significant difference in the general condition of the two groups. There was no significant difference in the clinical pregnancy rate (51.49% vs. 48.18%, p = 0.632) or the incidence of premature LH rise (18.81% vs. 15.45%, p = 0.584) between the two groups. However, the amount of Cetrotide used in the test group was significantly lower than that in the conventional dose antagonist group (1.13 ± 0.41 vs. 1.61 ± 0.59 mg, p < 0.001). Conclusion The flexible low-dose antagonist protocol and the conventional dose antagonist protocol were equally effective in people with a normal ovarian reserve in the fresh embryo transfer cycle of IVF-ET.