Context: In polycystic ovary syndrome (PCOS), an increased proportion of follicles leave the primordial (resting) pool and initiate growth. However there is little evidence for a reduced reproductive lifespan (early menopause) in women with PCOS, suggesting that the dynamics of follicle growth, and of follicle loss by atresia, are altered in PCOS.

Objective: The aim of this study was to investigate the possibility that loss of preantral follicles by atresia is reduced in PCOS, leading to prolonged follicle survival.

Design: Comparison of follicle growth in normal and polycystic ovaries using cultures of small ovarian biopsies.

Setting: Tissue samples obtained at routine laparoscopy from 12 patients with anovulatory PCOS and 16 controls, and processed in an ovarian physiology laboratory.

Main outcome measures: Morphometric analysis of follicle population in tissue fixed at time of biopsy (day 0) or after 5, 10 or 15 days in culture. Analyses included assessment of follicle and oocyte diameter, number and proportion of primordial and growing follicles, number and proportion of atretic follicles.

Results: In tissue fixed on day 0, the proportion of healthy growing follicles was, as expected, greater in ovaries from PCOS patients than in normal ovaries (64% vs 28%; p=0.0005) but there were no differences between PCOS and normal during culture. The rate of atresia throughout the period of culture in follicles was however significantly lower in PCOS tissue (p<0.0001). After culture 80% of follicles in normal ovarian tissue were atretic compared with 53% in PCOS biopsies.

Conclusion: Follicles from polycystic ovaries demonstrate a decreased rate of atresia in culture suggesting a mechanism for maintaining a larger follicle pool throughout reproductive life.