Abstract
Poor ovarian response (POR) patients often face the risk of not having enough competent oocytes. Then, aspirating small follicles could serve as a strategy to increase their number. Many efforts have been addressed to associate follicular size with oocyte competence, but results are controversial. Therefore, our study aimed to evaluate oocyte maturation and developmental competence, along with a non-invasive oocyte-maturation-related miRNA signature in oocytes retrieved from both large and small follicles. A total of 178 follicles, from 31 POR patients, were aspirated and measured on the day of ovarian puncture. Follicular diameters, oocyte collection, oocyte maturation, fertilization, blastocysts, and good-quality blastocyst rates were recorded. Simultaneously, follicular fluids were collected to quantify their miRNA expression. The efficacy of oocyte retrieval along with oocyte maturation, fertilization, and blastulation rates tended to increase with follicular size, but few significant differences were found. Despite there being significantly more collected oocytes from follicles > 11.5 mm compared to follicles ≤ 11.5 mm (p < 0.05), oocytes from the latter were also mature, with no significant differences in the miRNA signature, but only those > 13.5 mm demonstrated developmental competence. In conclusion, 11.5 mm follicles can produce mature oocytes, but only those larger than 13.5 mm yielded transferable embryos.