Low responders may benefit from undergoing ovarian stimulation with a long GnRH agonist protocol with corifollitropin alfa followed by hMG

To evaluate the outcomes of a long GnRH agonist protocol with corifollitropin alfa followed by hMG in low responders.

Retrospective cohort study. Patients with a suboptimal previous ovarian response (<9 oocytes) and a normal ovarian reserve (Poseidon groups 1 and 2) were classified in 1) Group 1 (n=88), submitted to a second cycle with a GnRH antagonist protocol using rFSH/hMG; 2) Group 2 (n=66), submitted to a long GnRH agonist protocol with corifollitropin alfa followed by hMG (named as simplified long protocol). Clinical outcomes were compared between groups and between the first/second cycle of each group.

Clinical outcomes were similar between groups. There were no differences in the number of oocytes [7(5-11.75) versus 7(5-10), p=0.802], clinical pregnancy (19.3% versus 18.2%, p=0.858) and live birth rates (18.2% versus 15.2%, p=0.619). However, baseline characteristics were different, decoding a poor prognosis among women in group 2. Both groups (1 and 2) had significantly higher number of oocytes, pregnancy, and live birth rates in the second cycle. In group 2, there was a higher rate of embryo transfer (56.1% versus 27.3%, p<0.001). In group 1, despite the similar rate of embryo transfer, there was a higher positive hCG (23.9% versus 8.0%, p=0.004).

Both simplified long protocol and GnRH antagonist protocol are suitable for low responders. The best second cycle clinical outcomes experienced in a population with worse prognosis (group 2) suggests that the simplified long protocol may be a better option, although prospective well-conducted studies must explore this hypothesis.