Because triple CGG repeats on FMR1 correlate with anti-Müllerian hormone, repeats may also correlate with clinical outcomes. In 55 in vitro fertilization patients, repeats, corrected for gonadotropin dosage, were, therefore, correlated to oocytes. Patients were stratified by <35 and > or =35 repeats, and by age to <38 or > or =38 years. Less than 35 (but not > or =35) repeats demonstrated significantly lower anti-Müllerian hormone at ages > or =38 than at <38 years ( P < .05). In >38 years, anti-Müllerian hormone was not affected by repeats. In <38 years, with <35 repeats (though not with > or =35), required significantly less gonadotropins than > or =38 ( P < .05). In <38 years (though not > or =38), those with <35 repeats produced significantly more oocytes than women with > or =35 repeats ( P = .006). In <38 years, retrieved oocytes were inversely related to repeats, adjusted for gonadotropin dosage ( P = .03). This supports FMR1 testing as useful in fertility practice and suggests why response rates to increasing stimulation with gonadotropins may vary.