Nondominant small follicles are a promising source of mature oocytes in modified natural cycle in vitro fertilization and embryo transfer

Objective To determine whether oocyte retrieval from nondominant small follicles supplies mature oocytes and increases live births in natural cycle IVF and embryo transfer (IVF-ET). Design Retrospective cohort study. Setting Private assisted reproductive technology practice. Patient(s) Seven hundred seventy-one infertile women who underwent natural cycle IVF between 2011 and 2013. Intervention(s) The LH surge was triggered via nasal buserelin when the dominant follicle reached 16–18 mm during nonstimulated cycles, and as many oocytes as possible were retrieved from nondominant small follicles (a diameter of 3–10 mm) after retrieval from the large (dominant) follicle. The embryos were cryopreserved once they had yielded good-quality blastocysts and then transferred (one per cycle) during subsequent cycles. Main Outcome Measure(s) Number of mature oocytes (metaphase II) and resulting live births yielded via oocyte retrieval from the initial cycle of treatment. Result(s) Among 771 women, nondominant small follicle puncture yielded 902 metaphase II oocytes and 78 live births, whereas large dominant follicle puncture yielded 466 metaphase II oocytes and 90 live births. Successes in oocyte retrieval and live births resulting from small follicle puncture were positively correlated with ovarian reserve but did not depend on the outcomes of the dominant follicle puncture. Conclusion(s) Nondominant small follicles are a promising supplementary source of mature oocytes for natural cycle IVF.