P-705 Influence of ovulation induction strategy in oocyte meiotic maturation: hCG versus agonist
Authors: Onofre Meza J , Schreurs I , Vanheusden E , Creemers E , Kerkhofs C , Dhont N 
Published: June 2022

Abstract

Study question
What is the influence of the ovulation induction strategy on the meiotic status of collected oocytes?

Summary answer
Non-invasive imaging of meiotic spindles during ICSI showed that ovulation induction with a hCG improved meiotic maturation and subsequent blastocyst formation rate.

What is known already
Owing to the shorter half-life of GnRH, this strategy has gained attention by significantly reducing risk of ovarian hyperstimulation syndrome. Reduced exposure to LH often requires luteal support and has been associated with a lower live birth rate, a lower ongoing pregnancy rate (pregnancy beyond 12 weeks) and a higher rate of early miscarriage (less than 12 weeks) in fresh autologous cycles, nevertheless. Mid-cycle LH surge triggers molecular activity in follicle cells initiating resumption of meiosis I for competition of the first meiotic division and formation of a MII oocyte inferring competence for subsequent fertilization and further development.

Study design, size, duration
A retrospective observational study was carried in a cohort of 25 - &gt; 36 years old women including 85 patients. Analysis was carried in two groups: 1: GnRHa trigger and 2: hCG trigger and later stratified for patient age.

Participants/materials, setting, methods
Women between 25 and &gt; 36 years old, non PCOS, with an AMH &gt; 1.2 ng/ml and stimulated under a short scheme GnRH-antagonist for downregulation, FSH and ovulation induction with GnRHa or hCG. Oocytes allocated to (intracytoplasmic sperm injection) ICSI treatment were cultured for 3-4 hours striped from cumulus cells 2 hours after retrieval and placed in G-MOPS PLUS in aglass bottom dish and with an Octax PolarAide system.

Main results and the role of chance
A spindle was present in 39.3% (218/554) of all morphologically mature (MII) oocytes alone. Group 1 (GnRHa trigger) and group 2 (hCG trigger) had 56% (309/554) and 44% (245/554) of oocytes at MII stage from which 38% (120/309) and 39% (96/245) showed spindles. A better meiotic maturation stage (scores 3, 4) at ICSI was found when ovulation induction was performed with hCG (group 2) (81% (98/120) versus 88% (85/96), p = 0,0031), nevertheless. Fertilization rate was no different between groups (60% and 58%, respectively), while significantly more blastocysts (at culture day 4 and 5) were generated from group 2 MII oocytes presenting a spindle and a good score (36% (35/98) versus 62% (53/85), p = 0.039). Good blastocyst quality (≥3BB) did not differ between groups. When stratifying for age, women between 25 – 30 presented no differences in presence or meiotic maturation (score 2, 3) in MII oocytes, while fertilization (42% versus 77%, p = 0.022) and blastocyst formation (32% versus 45%, p = 0.012) were better in group 2. Women between &gt; 36 years old presented no differences in presence of meiotic maturation, however, fertilization (40% versus 54%, p = 0.042) and blastocyst formation (25% versus 57%, p = 0.007) were best in group 2.

Limitations, reasons for caution
Thorough multivariable analysis in a larger patient cohort is required to endorse these results, nevertheless.

Wider implications of the findings
Prediction of ovulation induction efficacy in different patient cohorts could help fine tuning cycle management.

Trial registration number
not applicable