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.