Follicular flushing and in vitro fertilization outcomes in the poorest responders: a randomized controlled trial

STUDY QUESTION Does follicular flushing during oocyte retrieval improve the number of oocytes retrieved in the poorest responders? SUMMARY ANSWER Follicular flushing in the poorest responders does not increase the number of oocytes retrieved and may result in lower implantation and clinical pregnancy rates. WHAT IS KNOWN ALREADY Although previous studies have shown no beneficial effect of follicular flushing in normal responders, no study has demonstrated a detrimental effect and many IVF centers continue to perform this technique in poor responders. Data on follicular flushing in this patient group are limited, with no randomized trial to date assessing its utility in the poorest responders. STUDY DESIGN, SIZE, DURATION This randomized controlled trial compared the effects of follicular flushing and direct aspiration on IVF outcomes in the poorest responders, defined as having four or fewer follicles ≥12 mm on the day of hCG administration. Fifty patients were randomized during the 12-month enrollment period. PARTICIPANTS/MATERIALS, SETTING, METHODS The patients were treated at an academic fertility center at Weill Cornell Medical College, New York. MAIN RESULTS AND THE ROLE OF CHANCE Fifty women were randomized to follicular flushing (n = 25) or direct aspiration (n = 25). One patient in the direct aspiration group was canceled prior to oocyte retrieval for premature ovulation and was included in the intent-to-treat analysis. There was no difference in the number of oocytes retrieved with a median (IQR) of 4 (2–6) in the aspiration group versus 3 (2–5) in the flushing group (95% CI: −0.78, 1.98; P = 0.41). Patients who underwent follicular flushing had significantly fewer embryos transferred {1.7 [standard deviation (SD) 0.6] versus 2.5 (SD 1.2), P = 0.03}, a lower implantation rate (5.3 versus 34.2%, P = 0.006) and a lower clinical pregnancy rate (4 versus 36%, P = 0.01). The difference in pregnancy rates remained significant after adjusting for embryos transferred. LIMITATIONS, REASONS FOR CAUTION Findings, including results for secondary outcome measures, may not be generalizable to natural IVF cycles as these were excluded from the study. WIDER IMPLICATIONS OF THE FINDINGS This is the first randomized trial to evaluate the utility of follicular flushing in the poorest responders, and the first to demonstrate a potentially detrimental effect of flushing on IVF outcomes. STUDY FUNDING/COMPETING INTEREST(S) None. TRIAL REGISTRATION NUMBER NCT 01558141.