IMR Press / CEOG / Volume 48 / Issue 2 / DOI: 10.31083/j.ceog.2021.02.2284
Open Access Original Research
Time interval between hCG administration and oocyte pick up: analysis of oocyte maturation, embryonic morphology, morphokinetics, and IVF outcome
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1 Department of Obstetrics and Gynecology, Division Reproductive Endocrinology-IVF Carmel Medical Center, Bruce and Ruth Rappaport Faculty of Medicine, 3100000 Haifa, Israel
*Correspondence: (Sivan Skvirsky)
Clin. Exp. Obstet. Gynecol. 2021, 48(2), 402–409;
Submitted: 5 September 2020 | Revised: 1 December 2020 | Accepted: 4 December 2020 | Published: 15 April 2021
Copyright: © 2021 The Authors. Published by IMR Press.
This is an open access article under the CC BY 4.0 license (

Objective: To investigate associations of the time interval between hCG administration and oocyte pick up with oocyte maturation, embryonic morphology, morphokinetics, and IVF outcome, in different age groups. Design: A retrospective cohort study. Setting: An academic medical center. Patients: Women who underwent IVF and ICSI cycles in which all oocytes were incubated in a time lapse microscopy system (EmbryoScope). Cycles were stratified by age and time from hCG exposure. Interventions: None. Main Outcome Measures: Of 2185 IVF/ICSI OPU cycles, 820 cycles were included in the analysis. Final analysis was made on 796 cycles (4930 oocytes). Oocyte number and their maturity, fertilization rates, and embryo quality defined by morphology and morphokinetics, clinical pregnancy, and live birth rates. Results: The median hCG-oocyte pick up (OPU) interval was 34.45 hours. Among women over age 36 years, longer intervals were associated with both a higher fraction of mature oocytes (P < 0.008) and better morphology grading of embryos (P < 0.01). At all ages and all intervals, those with cleavage time, t2 27 hours achieved a statistically significant higher clinical pregnancy rate. No differences were found in morphokinetics (t2) between different hCG-OPU intervals for any of the age groups. Conclusions: Extending hCG to OPU interval may be beneficial for patients aged > 36 years, as more mature eggs and better embryo morphology were achieved. In older women with fewer oocytes retrieved, even a small extra number of mature oocytes may prove crucial for treatment outcome and improve success rates. A prospective, randomized study is warranted to determine whether optimal hGC-retrieval time interval merits revision/adjustment for older women.

Oocyte pick up
hCG interval
Mature oocytes
Embryo morphology
Fig. 1.
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