P-703 Is the time interval between triggering final oocyte maturation and oocyte retrieval associated with ART outcomes? A systematic review and meta-analysis
Authors: Deligeoroglou E , Bosdou J , Venetis C , Zepiridis L , Chatzimeletiou K , Grimbizis G , Kolibianakis E 
Published: July 2024

Study question

Is the time interval between triggering final oocyte maturation and oocyte retrieval associated with assisted reproductive technology (ART) outcomes?

Summary answer

Limited evidence suggests that extending the time interval between triggering final oocyte maturation and oocyte retrieval from 33-36h to 37-41h does not affect ART outcomes.

What is known already

The time interval between final oocyte maturation and oocyte retrieval varies among IVF centres, although an interval of 33–36 h is the most widely adopted. The use of a prolonged time interval of 37-41h has been suggested to increase the number and competence of oocytes retrieved, their maturation, their ability to be fertilized, their capacity to produce usable embryos and the probability of pregnancy. Considering recently published data, a systematic review is warranted to provide clinicians with updated, evidence-based information regarding the optimal time interval between triggering final oocyte maturation and oocyte retrieval.

Study design, size, duration

A systematic review and meta-analysis was performed aiming to evaluate the effect of the time interval between triggering final oocyte maturation and oocyte retrieval on ART outcomes. For this purpose, a literature search was carried out until January 2024 in PubMed, MEDLINE and CENTRAL.

The primary outcome measure was clinical pregnancy rate, while ovulation before oocyte retrieval, oocytes retrieved, maturation rate, fertilization rate, blastulation rate, implantation rate and miscarriage rate were secondary outcomes.

Participants/materials, setting, methods

Citation, demographic, methodological and clinical data were extracted from the studies by two independent reviewers. Quality was assessed using the RoB2 Tool by Cochrane. Statistical heterogeneity was assessed by I2. In dichotomous data, estimates were expressed as relative risk (RR) with 95% confidence intervals (CIs), using the fixed or random effects method. In continuous data, differences were pooled across resulting in a weighted mean difference (WMD) with 95% CI.

Main results and the role of chance

Six eligible RCTs (n = 1081) were identified, published between 1991-2023. In three trials, conventional insemination was used for fertilization, in two trials this was performed by intracytoplasmic sperm injection (ICSI), whereas in one trial either conventional insemination or ICSI were used. The time intervals between triggering final oocyte maturation and oocyte retrieval compared, varied between studies (34.5-36 vs 38.5-40h, 33 vs 41h, 34 vs 38h, 35 vs 37h, 34 vs 39h and 36 vs 38h). Patients were grouped in advance based on these time intervals (short interval group: 33-36h versus long interval group: 37-41h). Ovarian stimulation was performed with GnRH analogues (GnRH antagonists:1 GnRH agonists:5) and gonadotrophins (HMG:4 recombinant FSH:2, while triggering of final oocyte maturation was performed with hCG( recombinant hCG:1 urinary hCG:5). None of the studies was deemed as of low risk of bias.

No statistically significant differences were observed between the short nd long interval groups regarding clinical pregnancy rate per randomized patient (RR: 0.83; 95%CI: 0.62-1.11; fixed effects model; heterogeneity: I2:36.4%; five studies, 827 patients). Furthermore, it was not feasible to pool any of the secondary outcome data. This was either because they were not reported, or due to the fact that they were reported inappropriately.

Limitations, reasons for caution

This meta-analysis included a limited number of RCTs, which were generally of low quality due to methodological limitations and of high risk of bias. Moreover, the total number of patients is still not large enough to draw solid conclusions.

Wider implications of the findings

Taking into account the limitations of the current meta-analysis, it appears that clinicians may elect a shorter (33–36 h) or a longer (37-41h) interval regarding the timing of oocyte retrieval following triggering final oocyte maturation, without affecting clinical pregnancy rate.

Trial registration number

PROSPERO: CRD42024501986