Is there a benefit in follicular flushing in assisted reproductive technology?

Follicular flushing increases the number of oocytes retrieved: a randomized controlled trial

STUDY QUESTION

Does follicular flushing increase the number of cumulus-oocyte complexes (COCs) retrieved compared to single aspiration?

SUMMARY ANSWER

Follicular flushing significantly increases the number of COCs retrieved compared to single aspiration.

WHAT IS KNOWN ALREADY

On the basis of published meta-analyses, follicular flushing does not seem to increase the number of oocytes retrieved, the probability of clinical pregnancy, or that of live birth and has been associated with an increase in the duration of oocyte retrieval. It should be noted, however, that all the eligible randomized controlled trials (RCTs) in these meta-analyses have randomized patients into either single aspiration or follicular flushing. This study design might not allow the detection of the true effect of follicular flushing. Despite randomization, this might still be obscured, to an extent, by heterogeneity in patients, stimulation characteristics, and differences in the oocyte retrieval procedure.

STUDY DESIGN, SIZE, DURATION

A prospective, single centre, RCT, including 105 patients was performed between July and December 2022.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Eligible patients were those undergoing oocyte retrieval for ICSI, aged <43 years, with BMI 18-35 kg/m2. Patients with all types of ovarian response (low-normal-high), as assessed on the day of triggering final oocyte maturation, were included. Random allocation of the ovaries of each patient to either single aspiration or follicular flushing was performed on the day of oocyte retrieval, using a computer-generated randomization list. Patients could enter the study only once. All follicles from ovaries allocated to either follicular flushing or single aspiration, were aspirated by the same 16G double lumen needle, with a constant aspiration pressure of 190 mmHg, resulting in flow rate of 0.42 ml/s. In the ovaries allocated to the follicular flushing group, if a COC was not recovered in the initial aspirate of each follicle, follicular flushing was performed until a COC was retrieved, up to a maximum of five times. The primary outcome measure was the number of COCs retrieved. Secondary outcomes were oocyte recovery rate, oocyte maturation rate, fertilization rate, and rate of good quality embryos on Day 2. Values are expressed as a median (inter-quartile range).

MAIN RESULTS AND THE ROLE OF CHANCE

Significantly more COCs were retrieved in the follicular flushing as compared to the single aspiration group in all patients [5 (7) vs 2 (3), P < 0.001, respectively], as well as in patients with high [9 (3) vs 5 (4), P < 0.001, respectively], normal [5 (2) vs 2 (3), P < 0.001, respectively] and low [1 (1) vs 1 (1), P < 0.001, respectively] ovarian response. In patients with low ovarian response, no COCs were retrieved in 5.7% of the ovaries in the flushing group vs 42.8% of the ovaries in the single aspiration group (P < 0.001). The oocyte retrieval rate was significantly higher in the follicular flushing vs the single aspiration group, in all patients [88.9% (25.0) vs 45.5% (37.5), P < 0.001, respectively], as well as in patients with high [81.8% (15.9) vs 45.5% (22.2), P < 0.001, respectively], normal [85.7% (28.6) vs 40.0% (30.0), P < 0.001, respectively], and low [100% (0) vs 50.0% (100), P < 0.001, respectively] ovarian response. No significant difference was observed regarding maturation rate [85.2% (30.8) vs 100% (33.3), P = 0.78], fertilization rate [76.4% (50) vs 83.3% (50) P = 0.42], and the proportion of good quality embryos on Day 2 [83.3% (40) vs 100% (50), P = 0.62]. Similarly, no differences in the above variables were observed in patients with different types of ovarian response. Follicular flushing as compared to single aspiration was associated with a significant increase in the duration of oocyte retrieval in all patients [248 s (332) vs 135 s (164), respectively], as well as in patients with high [464 s (225) vs 237 s (89), P < 0.001, respectively], normal [248 s (108) vs 141 s (95), P < 0.001, respectively], and low [64 s (59) vs 48 s (10), P < 0.001, respectively] ovarian response.

LIMITATIONS, REASONS FOR CAUTION

Although the current study design allows for a more accurate evaluation of the true effect of follicular flushing on the number of COCs retrieved, it does not permit the evaluation of its role on the probability of pregnancy.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first RCT to suggest that follicular flushing increases the number of COCs retrieved compared to single aspiration, independently of ovarian response. This implies that follicular flushing plays an important role in the optimization of oocyte retrieval. These results, however, need to be confirmed in future studies, in which an equal flow rate should be used during oocyte retrieval.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was obtained for this study. There are no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

NCT05473455.

TRIAL REGISTRATION DATE

15 July 2022.

DATE OF FIRST PATIENT’S ENROLMENT

27 July 2022.

A Monocentric Randomized Controlled Clinical Trial to Compare Single- and Double-Lumen Needles in Oocyte Retrieval Procedure in Assisted Reproductive Technologies

The purpose was to determine any difference in outcomes, primarily in terms of number of retrieved oocytes per procedure, between two different needles used for oocytes retrieval procedure in Assisted Reproductive Technologies: the single-lumen needle (SLN) versus the double-lumen needle (DLN) with follicle flushing after aspiration. This randomized controlled trial included oocyte retrieval (OR) cycles for IVF and ICSI performed in 18 to 42-year-old women between March 2019 and January 2021 at a tertiary-care Fertility Center. A total of 200 ORs were randomized, 100 in each group. The mean number of retrieved oocytes was not different between groups (10.2 ± 6.5 for DLNs vs. 10.7 ± 7.0 for SLNs, p = 0.810). No significant differences were observed also in terms of number of retrieved oocytes/punctured follicles (83.0% ± 27.0% vs. 81.0% ± 22.0%, p = 0.916), number of retrieved oocytes/follicles at trigger (78.0% ± 29.0% vs. 78.0% ± 27.0%, p = 0.881), number of mature oocytes (7.6 ± 5.3 vs. 8.0 ± 5.1, p = 0.519), and pregnancy rate (27% vs. 23%, p = 0.514). However, the time required to retrieve each oocyte was longer using the DLN (1.5 ± 1.3 vs. 1.1 ± 0.9 minutes, p = 0.002). The present study confirmed the new perspectives on the sole use of SLNs in terms of saving time, without affecting the number of retrieved oocytes. Trial registration number and date of registration NCT03611907; July 26, 2018.

The importance of follicular flushing in optimizing oocyte retrieval

PURPOSE OF REVIEW

To critically evaluate the use of follicular flushing during oocyte retrieval.

RECENT FINDINGS

The latest meta-analysis evaluating follicular flushing does not favour its use over single aspiration. The randomized controlled trials (RCTs) included, however, are characterized by significant heterogeneity regarding the population analysed, the needle type and lumen used, the aspiration pressure applied and the number of flushing attempts performed. More importantly, information regarding the flow rate used for aspiration is scarce. The only RCT employing a constant flow rate between single aspiration and follicular flushing in women with monofollicular development, suggests that a higher number of oocytes is retrieved after follicular flushing.

SUMMARY

In order to eliminate clinical heterogeneity that might obscure the detection of the true effect of follicular flushing, randomization to single aspiration and follicular flushing should occur within the same patient. This can be achieved by randomly allocating each patient's ovary to either single aspiration or follicular flushing, maintaining similar flow rates between the groups compared.Given the importance of maximizing the number of oocytes retrieved from a given number of follicles developed, the conduction of properly designed RCTs evaluating follicular flushing is certainly required.

Does Oocyte Retrieval Performance in Mono-follicular Cycles Differ by Physician Experience?

Oocyte pick-up (OPU) is considered as a minor surgical procedure and complications are very rare when performed by trained physicians. However, data on training standards are limited and assessment of proficiency is challenging. The aim of this study was to show the impact of physician experience on OPU performance in mono-follicular in vitro fertilization (IVF) cycles, using two measurable outcome parameters: successful oocyte retrieval and operative time. Senior physicians (n = 6) had over 15 years of experience and novice physicians (n = 4) had at least 30 procedures under supervision. The study population included 226 mono-follicular cycles. Oocyte retrieval was successful in 179 out 226 procedures (79.2%); seniors and novices achieved similar oocyte retrieval rates (74.1%, 43/58 vs 80.9%, 136/168, p = 0.270). The mean duration of the procedure was 513.4 ± 163.1 (126-769) s. It was significantly shorter with a mean difference of - 117.9 s (95% CI: - 164.4 to - 71.3, p = 0.0001, Hedges g = 1.3) for senior physicians when compared to novices (425.8 ± 146.2 versus 543.7 ± 157.9 s). Novices who start performing OPU independently after 30 supervised procedures perform well in collecting the single oocyte grown in mono-follicular cycles; however, the mean duration of the procedure is relatively longer compared to seniors. After initial training period, physicians have few opportunities to compare themselves with their seniors and peers; periodical reassessment of the technique-which should also cover managing the operation time-would help confirm their own practices.

What is the optimum number of follicular flushes in mono-follicular in-vitro fertilization cycles in a poor responder population?

Objective:

Assessment of the optimal number of follicular flushes on retrieval rate and quality of oocytes in mono-follicular in-vitro fertilization (IVF) cycles.

Material and Methods:

A retrospective analysis of 246 oocyte pick-up procedures in mono-follicular IVF cycles of 226 poor responder women was performed. The primary endpoint was oocyte retrieval rate in the initial aspirate versus subsequent flushing episodes. The secondary endpoints were oocyte maturity, fertilization rates and embryo cleavage.

Results:

The procedure was successful in 187 cycles (76%), of which 160 metaphase-II oocytes were retrieved. Retrieval rates were similar for natural and modified natural cycles (p=0.595). The initial aspirate provided 54% of the total yield and the rest was obtained from up to four episodes of flushing. Follicular flushing increased oocyte recovery rate from 41.1% to 76%. None of the oocytes retrieved after three flushes fertilized. Oocyte maturity, fertilization and embryo cleavage rates were comparable for oocytes from the initial aspirate and one or two episodes of flushing. Oocytes obtained after the third flushing episode developed into poor quality embryos.

Conclusion:

Flushing confers a benefit for oocyte recover rates in mono-follicular IVF cycles in poor responder women. However, more than three attempts at flushing were not associated with good outcome.

Follicular flushing increases the number of oocytes retrieved in poor ovarian responders undergoing in vitro fertilization: a retrospective cohort study

Background

To investigate the impact of follicular flushing on the number of oocytes retrieved and embryo quality and to determine the optimal number of flushings for poor ovarian responders (PORs) undergoing in vitro fertilization (IVF).

Methods

This retrospective study included 291 IVF cycles in 224 patients who were PORs and had no more than three dominant follicles on retrieval day. During oocyte retrieval, follicular fluid was aspirated and examined for an oocyte. If no oocyte was identified, follicular flushing was repeated until an oocyte was retrieved or up to a maximum of nine times.

Results

The mean number of oocytes retrieved by aspiration and subsequent flushes was significantly higher than the number retrieved from the initial aspirate (1.73 ± 0.96 VS. 1.23 ± 1.00, P = 0.000). The total recovery rate was 83.7% (503/601), which was significantly higher than the 59.6% recovery rate for direct aspiration (P = 0.000). Before the 4th follicular flushing, the cumulative recovery rate increased significantly as flushing was repeated, but after the 4th flushing, the ascending trend was mitigated; and the risk ratio of recovering fewer oocytes after 4 flushes compared with after 9 flushes was 0.765 (95%CI, 0.570–1.026, P = 0.074). Significant differences were not observed in maturation rate, fertilization rate, cleavage rate or high-quality embryo rate (P > 0.05).

Conclusions

Follicular flushing may increase the number of oocytes retrieved and does not have adverse effects on oocyte or embryo quality in PORs undergoing IVF. Four times may be an optimal number of follicular flushings.

Comparison of costs associated with substituting culture medium with saline solution for follicular flushing during oocyte retrieval

OBJECTIVES

To compare culture medium and saline solution for follicular flushing during oocyte retrieval with assisted reproductive technologies.

METHODS

The present retrospective study analyzed data collected at Galway Fertility Clinic, Galway, Ireland, between January 1, 2015 and August 31, 2016; all patients attending the clinic for in vitro fertilization/intracytoplasmic sperm injection during this period were included. Data were stratified by whether follicular flushing was performed with culture medium or saline, and the oocyte yield rate, fertilization rate, embryo utilization rate, and biochemical and clinical pregnancy rates were compared between the groups.

RESULTS

In total, 422 oocyte retrieval procedures with culture medium and 277 with normal saline were analyzed. The fertilization (P=0.676) and clinical pregnancy rates (P=0.593) did not differ between the groups. Using normal saline resulted in an approximately 41-fold per-patient cost saving compared with culture medium.

CONCLUSION

Switching from culture medium to normal saline for follicular flushing significantly reduced oocyte-retrieval costs without adversely affecting reproductive outcomes.

Assisted reproductive techniques

Assisted reproductive technologies (ART) encompass fertility treatments, which involve manipulations of both oocyte and sperm in vitro. This chapter provides a brief overview of ART, including indications for treatment, ovarian reserve testing, selection of controlled ovarian hyperstimulation (COH) protocols, laboratory techniques of ART including in vitro fertilization (IVF), and intracytoplasmic sperm injection (ICSI), embryo transfer techniques, and luteal phase support. This chapter also discusses potential complications of ART, namely ovarian hyperstimulation syndrome (OHSS) and multiple gestations, and the perinatal outcomes of ART.

Impact of follicular G-CSF quantification on subsequent embryo transfer decisions: a proof of concept study

BACKGROUND

Previous experiments have shown that granulocyte colony-stimulating factor (G-CSF), quantified in the follicular fluid (FF) of individual oocytes, correlates with the potential for an ongoing pregnancy of the corresponding fertilized oocytes among selected transferred embryos. Here we present a proof of concept study aimed at evaluating the impact of including FF G-CSF quantification in the embryo transfer decisions.

METHODS

FF G-CSF was quantified with the Luminex XMap technology in 523 individual FF samples corresponding to 116 fresh transferred embryos, 275 frozen embryos and 131 destroyed embryos from 78 patients undergoing ICSI.

RESULTS

Follicular G-CSF was highly predictive of subsequent implantation. The receiving operator characteristics curve methodology showed its higher discriminatory power to predict ongoing pregnancy in multivariate logistic regression analysis for FF G-CSF compared with embryo morphology [0.77 (0.69–0.83), P < 0.001 versus 0.66 (0.58–0.73), P = 0.01)]. Embryos were classified by their FF G-CSF concentration: Class I over 30 pg/ml (a highest positive predictive value for implantation), Class II from 30 to 18.4 pg/ml and Class III <18.4 pg/ml (a highest negative predictive value). Embryos derived from Class I follicles had a significantly higher implantation rate (IR) than those from Class II and III follicles (36 versus 16.6 and 6%, P < 0.001). Embryos derived from Class I follicles with an optimal morphology reached an IR of 54%. Frozen-thawed embryos transfer derived from Class I follicles had an IR of 37% significantly higher than those from Class II and III follicles, respectively, of 8 and 5% (P < 0.001). Thirty-five per cent of the frozen embryos but also 10% of the destroyed embryos were derived from G-CSF Class I follicles. Non-optimal embryos appear to have been transferred in 28% (22/78) of the women, and their pregnancy rate was significantly lower than that of women who received at least one optimal embryo (18 versus 36%, P = 0.04).

CONCLUSIONS

Monitoring FF G-CSF for the selection of embryos with a better potential for pregnancy might improve the effectiveness of IVF by reducing the time and cost required for obtaining a pregnancy.

Follicular flushing during oocyte retrieval: a systematic review and meta-analysis

PURPOSE

The purpose of this systematic review and meta-analysis was to examine the literature and identify randomized controlled trials (RCTs), in order to answer if performing follicular flushing during the oocyte retrieval may improve the assisted reproductive technologies (ART) outcomes.

METHODS

An exhaustive electronic search was performed using MEDLINE and EMBASE databases. Only RCTs comparing follicular flushing to aspiration only during ART, were included. We included 5 trials, with a total of 482 patients randomized, with median ages ranging from 30.5 to 37.1.

RESULTS

The data analyses did not show significant differences regarding live birth rate, clinical pregnancies rates, and the number of oocytes retrieved. The duration of oocyte retrieval was significantly increased in the follicular flushing group.

CONCLUSIONS

The results from this systematic review and meta-analysis suggest that there is no advantage to use of routine follicular flushing during OR in an unselected group of patients.

The use of follicle flushing during oocyte retrieval in assisted reproductive technologies: a systematic review and meta-analysis

STUDY QUESTION

Does follicular flushing during assisted reproductive technologies (ART) improve the number of oocytes retrieved?

SUMMARY ANSWER

Follicular flushing during ART does not result in a greater number of oocytes in normal responders.

WHAT IS KNOWN ALREADY

Despite limited evidence supporting the use of follicular flushing, it continues to be a common procedure in many ART clinics. Prior studies have provided conflicting results regarding the routine use of flushing during oocyte retrieval.

STUDY DESIGN, SIZE, DURATION

Systematic review and meta-analysis of 518 patients who participated in 6 randomized trials over 20 years.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Literature searches were conducted to retrieve randomized controlled trials on follicle or ovarian flushing in ART. Databases searched included PubMed, EMBASE, Web of Science and the Cochrane Database of Clinical Trials (CENTRAL). Six trials that included 518 subjects matched the inclusion criteria. Studies included were limited to trials that were published, randomized trials comparing oocyte retrieval with a single-lumen pick-up needle versus follicle flushing after direct aspiration with a multi-channel oocyte pick-up needle in ART patients.

MAIN RESULTS AND THE ROLE OF CHANCE

In each of the trials, measures of the oocyte yield (oocytes retrieved divided by follicles aspirated), total oocytes retrieved, fertilization or pregnancy were not different when comparing direct aspiration with follicle flushing. Four trials reported a higher operative time with follicle flushing. Results of the meta-analysis indicated no significant differences in the oocytes retrieved [weighted mean difference: 0.07, 95% confidence interval (CI): -0.13 to 0.29] or the oocyte yield (odds ratio: 1.06, 95% CI: 0.95-1.18) between the non-flushing and flushing groups.

LIMITATIONS, REASONS FOR CAUTION

All trials featured an open label design and the majority of patients in this meta-analysis were normal responders. The applications of these results to poor responders, patients undergoing natural cycle ART or minimal stimulation ART should be made with caution.

WIDER IMPLICATIONS OF THE FINDINGS

Follicle flushing does not improve ART outcomes in normal-responding patients and should not be performed. This meta-analysis should solidify this recommendation as it includes the largest trial published on the subject and is consistent with a recently published Cochrane review.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported, in part, by the Program in Reproductive and Adult Endocrinology, NICHD, NIH, Bethesda, MD. The authors have no competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.