Differences in ovarian function parameters between Chinese and Caucasian oocyte donors: Do they offer an explanation for lower IVF pregnancy rates in Chinese women?

BACKGROUND: IVF outcomes in Chinese women are inferior to those of Caucasian patients. Reflecting prematurely diminished ovarian function, women with elevated age-specific baseline (b-) FSH levels are designated to suffer from premature ovarian aging (POA). We investigated if the prevalence of POA differs between these two ethnic populations. METHODS: We compared patient characteristics and first IVF cycle outcomes in 29 consecutive, Caucasian and 17 Asian-Chinese oocyte donors. POA was diagnosed in a donor if her b-FSH levels exceeded the 95% confidence interval (CI) for her age group. RESULTS: There was no age difference between Chinese and Caucasian groups (26.2 ± 4.9 versus 25.7 ± 3.1 years, respectively). Chinese women demonstrated, however, a higher cycle cancellation rate (5/17, 29.4%), either before cycle start or during stimulation (0/29; relative risk 1.42, 95% CI 1.04-1.9; P < 0.01), fewer oocytes per initiated cycle (9.3 ± 9.7 versus 15.3 ± 7.1, respectively; P < 0.05) (difference disappeared for only cycles that reached retrieval) and higher b-FSH levels (7.5 ± 1.9 versus 5.1 ± 1.7 mIU/ml, respectively; P = 0.004). Nine out of 17 (53%) of Chinese and only 1/26 (4%) of Caucasian donors met b-FSH level criteria for a presumptive POA diagnosis. Their odds of meeting POA criteria were approximately 30-times greater (odds ratio 31.5; 95% CI 3.5-18.7; P < 0.0001). CONCLUSIONS: These data suggest a possible explanation for lower IVF pregnancy rates in Chinese women. Preceding treatment, Chinese women at all ages should be carefully investigated to detect occult POA. Ethnicity may have to be considered an additional outcome variable in fertility studies.