Impact of Systematic Follicular Flushing on Egg Retrieval and Embryo Quality in IVF-ICSI Cycles: A Controlled Study?

Background/Objectives: Ultrasound-guided transvaginal follicular aspiration is a central procedure in in vitro fertilisation (IVF), aiming to collect oocytes necessary for the success of assisted reproduction treatments. Follicular flushing, proposed in the absence of cumulo-oocyte complex (COC) at initial aspiration, remains controversial regarding its real impact on oocyte quality and pregnancy rates. Methods: In this controlled study, conducted in 274 patients, we evaluated the effects of systematic follicular flushing up to 10 washes with a standardised medium (pH 7.3 ± 0.1; 37.2 ± 0.2 °C) on oocyte yield, oocyte morphology, embryo kinetics and clinical outcomes. Results: Flushing resulted in an additional 38% recovery of COCs, mostly between the second and fifth flush, with no significant increase in oocyte dysmorphisms or major embryonic abnormalities. A slight increase in slow cleavages was observed (27% vs. 23%, p = 0.04), as well as a lower oocyte maturation rate when ovulation was triggered by Ovitrelle alone. Clinically, pregnancy rates per transfer were comparable between groups (33.27% without flushing vs. 32.86% with flushing; p = 0.67), as were miscarriage rates (9.11% vs. 8.69%; p = 0.81). Conclusions: These results indicate that follicular flushing, when applied according to a standardised protocol, significantly increases oocyte yield without compromising oocyte morphological quality or embryonic development potential. Although the observed clinical benefits remain modest, this approach could constitute a relevant complementary strategy, particularly in patients with poor ovarian response or in the context of poor initial recovery. However, the controlled but non-randomised nature of this study requires cautious interpretation of the findings. Larger randomised trials, integrating dynamic assessment technologies, such as time-lapse imaging or oocyte transcriptomic analysis, are needed to refine the clinical indications of this technique and explore its underlying biological mechanisms.