A systematic review and meta-analysis of randomized controlled studies comparing follicular flushing versus aspiration during oocyte retrieval in IVF cycles.

Objectives: To assess the value of follicular flushing during ovum pick up compared to follicular aspiration in IVF cycles.

Search strategy: Screening of PubMed, Web Of Science, Cochrane, Scopus, and clinical trials registry from inception to October 2024. The search key words included follicular flushing, follicle aspiration, ovum pick up, oocyte retrieval, IVF, and their MeSH terms.

Selection criteria: This review included all RCTs that evaluated the use of follicular flushing during ovum pick-up. Seventeen studies including 2218 participants (1124 were subjected to follicular flushing and 1094 subjected to follicular aspiration) were included.

Data collection and analysis: The extracted data included the settings of the study, the number and characteristics of participants, intervention details including the number of flushes, and the suction pressure used, outcome parameters including number of retrieved oocytes, the oocyte/ follicle ratio, the number of MII oocytes, the time of the procedure, the fertilization, implantation, clinical pregnancy, chemical pregnancy, ongoing pregnancy, live birth, miscarriage and cancellation rates, and risk of bias assessment.

Main results: The number of retrieved and MII oocytes were evaluated in 14 and 11 studies with 1920 and 1588 participants and revealed a mean difference (MD) of 0.03 and 0.16 with [-0.50, 0.57] and [-0.29, 0.61] 95% CI (P value =0.9 and 0.48, I² = 87% and 90%), respectively. The fertilization and implantation rates were evaluated in 4 and 7 studies with 3331 and 1605 participants and revealed an Odd Ratio (OR) of 1.48 and 0.91 with [0.98, 2.24] and [0.55, 1.51] 95% CI (P value =0.06 and 0.72, I² = 82% and 61%), respectively. The clinical pregnancy rate was evaluated in 11 studies with 1542 participants and revealed an Odd Ratio (OR) of 1.23 with [0.86, 1.74] 95% CI (P value =0.26, I² = 42%). The ongoing pregnancy /livebirth rate was evaluated in 11 studies with 1266 participants and revealed an Odd Ratio (OR) of 1.07 with [0.80, 1.43] 95% CI (P value =0.65, I² = 0%). The time of the procedure was evaluated in 8 studies with 985 participants and revealed a mean difference (MD) of 178.58 with [98.23, 258.93] 95% CI (P value <0.001, I² = 97%). The cycle cancellation rate was evaluated in 5 studies with 856 participants and revealed an Odd Ratio (OR) of 0.66 with [0.45, 0.98] 95% CI (P value =0.04, I² = 0%).

Conclusion: Follicular flushing during oocyte retrieval did not improve the number of retrieved oocytes, the oocyte retrieved over the aspirated follicles ration, the number of MII oocytes, the fertilization rate, implantation rate, clinical pregnancy, chemical pregnancy, ongoing pregnancy/livebirth, and miscarriage rates and associated with significant prolongation of the procedure. Cycle cancellation was significantly improved with follicular flushing in women with poor ovarian response.

Trial registration: Registration number CRD42024600698 date of registration 23/10/2024.