The effect of ovarian follicle size on oocyte and embryology outcomes

Abstract

Objective: To identify relationships between the size of punctured ovarian follicles and subsequent embryology outcomes.

Design: Prospective observational cohort study.

Setting: Private fertility center.

Patients: One hundred fifty-seven oocyte retrievals performed during the study period.

Interventions: The diameter of punctured follicles was ultrasonically measured during routine oocyte collection. The resulting embryos were group-cultured to the blastocyst stage and classified into 8 groups according to follicle size (≤9.5, 10-12.5, 13-15.5, 16-18.5, 19-21.5, 22-24.5, 25-27.5, and ≥28 mm).

Main outcome measure: Rate of good-quality blastocysts per follicle puncture.

Results: This study included 4,539 follicle punctures, 2,348 oocytes, 1,772 mature oocytes, 1,258 bipronuclear (2pn) oocytes, and 571 good-quality blastocysts derived from 157 oocyte retrievals. The per-puncture yields of oocytes, mature oocytes, 2pn oocytes, and good-quality blastocysts were associated with the size of the punctured follicle. The rates of good-quality blastocysts per punctured follicle were 2.2% (≤9.5 mm), 6.2% (10-12.5 mm), 11.9% (13-15.5 mm), 14.5% (16-18.5 mm), 18.9% (19-21.5 mm), 17.5% (22-24.5 mm), 15.9% (25-27.5 mm), and 16.0% (≥28 mm). When compared with the overall average, punctures of follicles in groups ≤12.5 mm in diameter had significantly inferior yields of good-quality blastocysts, whereas punctures of follicles in groups 19-24.5 mm in diameter were associated with significantly greater than average yields of good-quality blastocysts. Other groups did not differ significantly from average. No correlation was observed between follicle diameter and ploidy of biopsied blastocysts.

Conclusions: Punctures of follicles ≤12.5 mm in diameter rarely result in good-quality blastocysts. The yield of good-quality blastocysts progressively increases with follicle size up to approximately 19 mm in diameter, with no substantial decline above that size. The ploidy of the blastocysts that form appears to be unaffected by follicle size.

Keywords: Aneuploidy; blastocyst; follicle size; oocyte maturity; ovarian follicles.