HCG (1500IU) administration on day 3 after oocytes retrieval, following GnRH-agonist trigger for final follicular maturation, results in high sufficient mid luteal progesterone levels - A proof of concept

Background: Controlled ovarian hyperstimulation (COH) which combining GnRH antagonist co-treatment and GnRH agonist trigger with an additional 1500 IU hCG luteal rescue on day of oocytes retrieval, has become a common tool aiming to reduce severe ovarian hyperstimulation syndrome (OHSS). In the present, proof of concept study, we evaluate whether by deferring the hCG rescue bolus for 3 days, we are still able to rescue the luteal phase. Methods. Patients undergoing the GnRH-antagonist protocol, who were considered at high risk for developing severe OHSS and received GnRH-agonist for final oocyte maturation, were included. For luteal phase support, all patients received an "intense" luteal support. Those who had no signs of early moderate OHSS on day 3 after oocytes retrieval were instructed to inject 1500 IU of HCG bolus (hCG group). Ovarian stimulation characteristics and mid luteal progesterone levels were compared between those who received the HCG bolus and those who did not. Results: Eleven IVF cycles were evaluated, 5 in the hCG group and 6 in the intense luteal support only group. While no in-between group differences were observed in ovarian stimulation characteristics, significantly higher mid luteal progesterone levels (>127 nmol/L vs 42.1 ± 14.5 nmol/L, respectively) and a non-significant increase in pregnancy rate (40% vs 16.6%, respectively), were observed in those who receive the hCG bolus compared to those who did not. Conclusions: hCG luteal rescue should be offered 3 days after oocytes retrieval only to those patients with no signs of early moderate OHSS. Further studies are required to elucidate the appropriate regimen of luteal HCG administration in patients undergoing final follicular maturation with GnRH-agonist.