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Timing of Oocyte Retrieval Can Determine Outcome of In Vitro Fertilisation: Presented at ASRM

By Arushi Sinha

SAN FRANCISCO -- November 13, 2008 -- Fertilisation and pregnancy rates can be improved by delaying oocyte retrieval from 34 to 37 hours, researchers reported here at the American Society for Reproductive Medicine (ASRM) 64th Annual Meeting.

For patients undergoing fertility treatment, timing is often a key element in determining successful outcomes. Research presented examined if the difference of just a few hours may ultimately impact pregnancy rates.

"We performed oocyte retrieval at 34 hours and at 37 hours after hCG [human chorionic gonadotropin] dosing," explained Ju Hee Lee, MS, Laboratory of In Vitro Fertilisation (IVF), Mirae & Heemang OB/GYN Clinic, Seoul, Korea, who presented the findings on November 11 on behalf of the research team.

The prospective, randomised study compared clinical outcomes for oocyte retrieval at 34 and 37 hours subsequent to hCG administration. The goal was to increase the uptake of the mature oocyte, according to co-author Jive Jung, MD, Laboratory of IVF, Mirae & Heemang OB/GYN Clinic.

They randomised 89 women into 2 treatment cohorts: 52 women underwent oocyte retrieval 34 hours after hCG administration; 37 women underwent oocyte retrieval 37 hours after hCG administration.

Patients groups were compared with respect to number of oocytes, fertilisation rate, and pregnancy rate, among other parameters. The 2 groups were similar for mean number of ampules needed for stimulation, duration of infertility, and number of previous IVF attempts.

The results demonstrated that the average number of oocytes was lower in the group that underwent oocyte retrieval at 34 hours than in the 37-hour group (10.33 vs 15.51).

Possibility of cryopreservation of embryos was greater in the 37-hour cohort than in the 34-hour cohort (65% vs 25%). However, the researchers found little difference between either of the 2 groups with regards to the proportion of potentially viable embryos or the cumulative embryo score.

Based on these findings, the authors concluded that increasing the time to 37 hours from the point of hCG administration increased the number of oocytes that can be retrieved for the purpose of cryopreservation. Over time, the increase is reflected in the cumulative pregnancy rate.

"By increasing the maturity of the oocyte, we can ultimately increase the fertilisation and pregnancy rates," summarised Dr. Lee.

[Presentation title: Clinical Outcome of Extending the Interval Between Human Chorionic Gonadotropin Administration and Oocyte Retrieval in IVF-ET. Abstract P-377]

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