P–155 Oocyte recovery 39 hours (from 39h to 41h) after administration of follicular maturation trigger does not affect clinical results

Study question What is the clinical outcome of oocytes recovered after 39 hours from ovulation inducing drug administration? Summary answer Oocytes obtained after 39 hours from follicular maturation triggering are equally viable to those obtained at the standard time of 36 hrs. What is known already In the clinical setting of ART, ovum pick-up (OPU) is generally performed around 36 hours after the administration of ovulation inducing drugs (OID). However, there are cases where OPU cannot be performed at this time often due to long operating lists. As the time elapsed between the administration of ovulation inducing drugs and OPU becomes longer, there is a concern about time-related oocyte aging. Nevertheless, there are few reports of clinical results of OPU after 36 hours from OID. Study design, size, duration We conducted a review of 1187 cycles and 1951 patients in which OPU and embryo transfer was performed in 2017–2018. All cycles underwent a ‘freeze-all’ of embryos and the transfer cycle was in the thawed embryo transfer cycle for all cases. Participants/materials, setting, methods The time from the administration of OID to the end of OPU was divided into 36h group and over 39h group and the MII and normal fertilization rate of oocytes obtained from OPU after ovarian stimulation were compared. After confirmation of fertilization, the D3 good-quality embryo and the D5 and 6 good-quality blastocyst rates of embryos that continued to be cultured and the pregnancy and miscarriage rates of cleavage-stage embryos and blastocyst transfers were compared. Main results and the role of chance The MII rate in the 36h and >39h groups was 78.1% vs. 80.0%, and the normal fertilization rate was 77.9% vs. 78.1% (ICSI) and 65.4% vs. 67.6% (Conventional-IVF). The D3 good-quality embryo rate (good-quality embryos are embryos with less than 5% fragmentation in 7–9 cells and compaction with more than 50% adhesion between split spheres) was 21.8% vs. 25.3%, the D5 good-quality blastocyst rate (at least 3BB according to Gardner classification) was 33.6% vs. 40.1%, and the D6 good-quality blastocyst rate was 31.1% vs. 37.5%, all of which were not significantly different. The pregnancy rate for cleavage-stage embryo transfer was 26.6% vs. 6.7%, and the miscarriage rate was 25.3% vs. 42.9%, both of which were not significantly different. The pregnancy rate for blastocyst transfer was 45.4% vs. 50.0%, and the miscarriage rate was 22.2% vs. 20.0%, both of which were not significantly different. (The significance difference test was a χ-square test) Limitations, reasons for caution The study was a retrospective study. Wider implications of the findings: Even if OPU is conducted after 36h of the administration of OID, to the extreme range of 39h–41h, oocyte aging does not seem apparent and pregnancy outcomes are similar to the standard time interval of 36 hours. Trial registration number ‘not applicable’