Low dose hCG supplementation in a Gn-RH-agonist trigger protocol is associated with worse pregnancy outcomes: a retrospective cohort study.

Background: A number of studies have looked at dual triggers with hCG and GnRH agonist (GnRHa) in varying doses, but the question remains: what is the optimal dose of hCG to minimize ovarian hyperstimulation syndrome (OHSS) and still offer adequate pregnancy rates? The purpose of this study was to compare pregnancy and OHSS rates following dual trigger for oocyte maturation with GnRHa and a low-dose hCG versus hCG alone. A secondary objective was the assess pregnancy outcomes in subsequent frozen cycles for the same population.

Methods: A total of 963 women < 41 years old, with a BMI 18-40 kg/m and an AMH > 2 ng/mL who underwent fresh autologous in vitro fertilization (IVF) with GnRH antagonist protocol at a University-based fertility center were included in this retrospective cohort study. Those who received a low dose dual trigger with hCG (1000u) and GnRHa (2 mg) were compared to those who received hCG alone (10,000u hCG/250-500 μg Ovidrel). Differences in implantation rates, pregnancy, live birth, and OHSS were investigated.

Results: The dual trigger group was younger (mean 33.6 vs 34.1 years), had a higher AMH (6.3 vs 4.9 ng/mL,) more oocytes retrieved (18.1 vs 14.9) and a higher fertilized oocyte rate (80% vs 77%) compared with the hCG only group. Yet, the dual trigger group had a lower probability of clinical pregnancy (gestational sac, 43.4% vs 52.8%) and live birth (33.4% vs 45.8%), all of which were statistically significant. There were 3 cases of OHSS, all in the hCG-only trigger group. In subsequent frozen cycles, pregnancy rates were comparable between the two groups.

Conclusions: The dual trigger group had a better prognosis based on age and AMH levels and had better stimulation outcomes, but significantly worse pregnancy outcomes, suggesting the low dose hCG (1000u) in the dual trigger may not have provided adequate luteal support, compared to an hCG-only trigger (10,000u hCG/250-500 μg Ovidrel). Interestingly, the pregnancy rates were comparable in subsequent frozen cycles, further supporting the hypothesis that the issue lies in inadequate luteal phase support, rather than embryo quality. Based on these findings, our program has changed the protocol to 1500u of hCG in a dual trigger.