Some Delay in Oocyte Retrieval and ICSI has No Impact on Live Birth Rates

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Some delay in oocyte retrieval and ICSI has no impact on live birth rates

Expanding the time interval between ovulation triggering and oocyte injection: does it affect the embryological and clinical outcome?

A single centre retrospective study of couples undergoing artificial cycles (ICSI) was conducted to evaluate what effect does a greater time interval, between ovulation triggering to collection to sperm injection, has on embryo and clinical outcomes in ICSI cycles.

Most experts agree that somewhere from 38 to 39 hours post ovulation triggering (hCG or GnRH agonist) is the optimal time however in busy Assisted Reproductive Technology centres this is apparently challenging. To analyse this, 8811 ICSI cycles between 2010 to 2015 were included in this study. Cycles were catergorised into seven groups: <36 hours, 36 hours, 37 hours, 38 hours, 39 hours, 40 hours and ≥ 41hours, with fertilized embryos then transferred on Day 3 (64.6%) or 5 (28.5%).

In order to reduce possible confounding factors, the exclusion criteria included: injection with testicular or epidydimal sperm, conventional IVF, combined conventional IVF/ICSI, preimplantation genetic testing and IVM cycles. Clinical pregnancy was defined as detection of foetal heart beat 7 weeks post embryo transfer, with delivery of a live born at 24 weeks of gestation or later classified as a live birth.

Initial unadjusted analysis showed maturation and fertilization rates increased, 77.1 to 82.2% and 68.2 to 79.3% respectively, with increasing time (<36 hours to ≥ 41 hours). However embryo utilization rates, in either Day 3 or Day 5 embryos, did not differ significantly between the 7 time interval groups. After adjustment for other confounding factors, maturation and fertilization rates still showed a significant upward trend with time, although this had no impact on utilization rates.

Further analysis showed the overall unadjusted average clinical pregnancy rates was 28.4% and 46.7%, for Day 3 and Day 5 embryo transfers respectively. Following this, unadjusted live birth rates, for Day 3 and Day 5 embryo’s, was 20.3% and 37.5% respectively. Interestingly, both unadjusted and adjusted analysis showed no significant difference between the 7 groups, in either pregnancy or live birth rates, for Day 3 and Day 5 embryos.

The author noted that patients in the <36 hour group showed a progressive decline in outcomes, with slightly lower maturation and fertilization rates, leading to a clear drop in pregnancy and live birth rates, although statistical significance was not achieved, due to the limited sample size of this group.

Caution is advised by the author extrapolating these results to other Assisted Reproductive Technologies such as conventional IVF, IVM or injection with testicular / epidydimal sperm.


This study of 8811 women undergoing ICSI, found that ART clinics running late for egg retrieval, up to 41 hours post ovulation triggering, had no significant impact on the rate of embryo maturation, fertilization, pregnancy and live births, with either day 3 or day 5 transferred embryos.


  1. Limited sample size in < 36 hour group
  2. Retrospective study over 5 years
  3. Injection timing was only recorded per cycle and not oocyte, influencing a limited number of cases (172/8811)
  4. Cumulative pregnancy and live birth rates not tracked

Similar studies

Maggiulli R, et al. (2020). The effect of ICSI-related procedural timings and operators on the outcome.

Shen X, et al. (2019). Optimal Ovulation Trigger-Oocyte Pickup Interval in Progestin-Primed Ovarian Stimulation Protocol: A Retrospective Study Using Propensity Score Matching.

Bárcena P, et al. (2016). Should we worry about the clock? Relationship between time to ICSI and reproductive outcomes in cycles with fresh and vitrified oocytes.

Bosdou J K, et al. (2015). Is the time interval between HCG administration and oocyte retrieval associated with oocyte retrieval rate?

Garor R, et al. (2015). Prolonging oocyte in vitro culture and handling time does not compensate for a shorter interval from human chorionic gonadotropin administration to oocyte pickup.


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