P-771 Does follicle size impact effect of follicular flushing on oocyte retrieval rate and embryology outcomes?
Authors: Ghumman S , Batra A , Khanna S , Patel S , Gupta M 
Published: July 2024

Abstract

Study question
Is the effect of follicular flushing on oocyte retrieval rate (RR) and embryology outcome influenced by follicular size?

Summary answer
Flushing improved RR in discordant growth with smaller(8-12 mm) follicles and larger(&gt;22mm) follicle. Flushing did not impact embryological outcomes adversely. It increased top quality embryo

What is known already
Follicular flushing is done in poor responder for improving retrieval rate. There are very few studies in normal or hyper responders. Studies show controversial results of flushing, some showing benefits, while others, a detrimental effect because of increased intra-follicular pressure, increased procedure time, and change in paracrine milieu of oocytes by dilution with flushing medium No study has addressed whether increased retrieval rates with flushing are dependent on follicular size and indirectly maturity of oocyte. Most studies flushed with fixed volume of 1-2ml as size of follicle was not taken into account, making volume inadequate for completely flushing larger follicles.

Study design, size, duration
Prospective cohort study conducted from September 2022 to August 2023.
Group 1: Study group- follicles were flushed after aspiration. Total patients were 120. They were divided into 3 groups according to follicular size and fluid volume aspirated with sample size calculated as
A:306 small follicles 8-12 mm(&lt;1.0ml),
B:467 medium follicles 13-22 mm (1.0-6.0ml)
C:102 large follicle &gt; 22 mm (&gt;6.0 ml).
Group 2- Control group where follicles aspirated without flushing in 280 patients, 2572 follicles.

Participants/materials, setting, methods
Ethical approval taken.
Inclusion - patients 21-40years of age undergoing oocyte retrieval for IVF/ICSI cycle with antagonist protocol
Exclusion of oocyte of indeterminate origin ie one aspirate have two oocytes
Group1 After aspiration of follicle with double lumen oocyte retrieval needle, follicle flushed with media volume equivalent to follicular volume. Group2 only follicular aspiration and volume measured
Analysis done using SPSS-25 version.
Primary outcome retrieval rate(RR) of oocytes. Secondary outcome: fertilization rate, percentage of top quality embryos(TQE)on day3&5, blastocyst rate.

Main results and the role of chance
Flushing follicle significantly increased RR in smaller follicles(8-12mm) compared to controls 159/311 (51.12%)vs 176/780 (22.56%) p = &lt;0.001 and also in larger follicles(&gt;6ml) 76/109 (69.72%)vs 116/219 (52.96%) p = &lt;0.01 No difference seen in optimum size follicles (13-22mm) 337/470 (71.7%)vs 1099/1573(69.86%) p = 0.44. Overall, there was statistically significant increase in RR with flushing 567/890 (63.7%)vs 1391/2572 (54.08%) p = &lt;0.001. Significantly more time was taken for flushing vs control groups 16.50vs 12.15 minutes p = &lt;0.001. Secondary outcomes like fertilization rate was not different with flushing 476/567 (83.95±15.01%)vs 1125/1391(80.88±19.01 %) p = 0.21. Percentage of TQE (day 3) were significantly more in flushing group 321/476 (67.43±25.41%)vs control 642/1125 (57.07±25.94%)p = &lt;0.01. TQE (day 5) were significantly more in flushing group 142/476 (29.83±11.02)vs control 251/1125 (22.31±12.11%)p=0.04. Blastocyst rate remained similar in both groups 196/476 (41.18±16.73 %) vs 403/1125 ( 35.82±13.90 %) p = 0.12.
Subgroup analysis showed that younger women (&lt;35yrs)had a significantly higher RR with flushing 66.33±16.29%vs controls 57.88±13.68% (p = &lt;0.01), compared to older women &gt;35 years 60.29±16.37%vs 56.35±17.30% (p = 0.38). Women with higher AMH had better RR with flushing 63.71±15.11%vs controls 56.50±14.33 (p = 0.01) compared to women with lower AMH (&lt;1 ng/ml) where flushing made no difference 63.47±19.59%vs 60.62±14.93(p = 0.79). Normal and hyper responders had significantly higher RR with flushing 66.16±15.11vs controls 57.53±13.85%(p = &lt;0.001) compared to poor responders (&lt;5 oocytes) 51.07±18.07vs 56.24±27.47(p = 0.55).

Limitations, reasons for caution
Although RR was better with flushing in small and large follicles we could not translate the advantage to pregnancy rate(PR) PR could not be calculated as some patients wanted 2 embryos transferred. Since patient had one each embryos from small and optimum follicles both were transferred. Further RCT required.

Wider implications of the findings
Practice of follicular flushing needs re-evaluation
Women with discordant growth should be taken for flushing as it increases RR in small and large follicles
Role of flushing should be widened beyond poor responders to younger women, with normal or hyper response increasing oocyte yield which may increase cumulative pregnancy rate

Trial registration number
not applicable