The effect of CGG repeat number on ovarian response among fragile X premutation carriers undergoing preimplantation genetic diagnosis

Objective: To assess ovarian response among carriers of FMR1 premutation who undergo preimplantation genetic diagnosis (PGD). Design: Retrospective study. Setting: Academic IVF unit. Patient(s): Of 18 carriers of FMR1 premutation referred to PGD, eight had <100 CGG repeats and ten had ≥100 CGG repeats. Intervention(s): Controlled ovarian stimulation (COH) and PGD. Main Outcome Measure(s): Correlation between the number of CGG repeats and the level of E₂ at day of hCG administration, number of retrieved oocytes, number of two-pronuclear (2PN) zygotes, and dose of recombinant FSH. Result(s): There was a positive correlation between CGG repeats and the level of E ₂ at day of hCG administration, number of retrieved oocytes, and number of 2PN zygotes. There was a negative correlation between number of CGG repeats and the total dose of gonadotropins. The E₂ level and the number of retrieved oocytes and 2PN zygotes were significantly higher and the dose of gonadotropins significantly lower for premutation patients with ≥100 CGG repeats compared with <100 CGG repeats. Conclusion(s): There is a positive correlation between E₂ level, retrieved oocytes, 2PN zygotes, and number of CGG repeats. Premutation carriers with <100 CGG repeats suffer from impaired ovarian response and decreased fertilization rate.