Attitudes towards potentially carrying the FMR1 premutation: before vs after testing of non-carrier females with diminished ovarian reserve

Distribution of the FMR1 gene in females by race/ethnicity: women with diminished ovarian reserve versus women with normal fertility (SWAN study)

OBJECTIVE

To study whether reported, but inconsistent, associations between the FMR1 CGG repeat lengths in the intermediate, high normal, or low normal range differentiate women diagnosed with diminished ovarian reserve (DOR) from population controls and whether associations vary by race/ethnic group.

DESIGN

Case-control study.

SETTING

Academic and private fertility clinics.

PATIENT(S)

DOR cases (n = 129; 95 Whites, 22 Asian, 12 other) from five U.S. fertility clinics were clinically diagnosed, with regular menses and no fragile X syndrome family history. Normal fertility controls (n = 803; 386 Whites, 219 African-Americans, 102 Japanese, 96 Chinese) from the United States-based SWAN Study had one or more menstrual period in the 3 months pre-enrollment, one or more pregnancy, no history of infertility or hormone therapy, and menopause ≥46 years. Previously, the SWAN Chinese and Japanese groups had similar FMR1 CGG repeat lengths, thus they were combined.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

FMR1 CGG repeat lengths.

RESULT(S)

Median CGG repeats were nearly identical by case/control group. DOR cases had fewer CGG repeats in the shorter FMR1 allele than controls among Whites, but this was not significant among Asians. White cases had fewer CGG repeats in the shorter allele than Asian cases. No significant differences were found in the high normal/intermediate range between cases and controls or by race/ethnic group within cases in the longer allele.

CONCLUSION(S)

This study refutes prior reports of an association between DOR and high normal/intermediate repeats and confirms an association between DOR and low normal repeats in Whites.

The FMR1 gene, infertility, and reproductive decision-making: a review

The strongest association between FMR1 and the ovary in humans is the increased risk of premature ovarian failure (POF) in women who carry the premutation level of CGG repeats (55–199 CGGs). Research on the FMR1 gene has extended to other endpoints of relevance in the OB/GYN setting for women, including infertility and ovarian hormones. After reviewing the nomenclature changes that have occurred in recent years, this article reviews the evidence linking the length of the FMR1 repeat length to fertility and ovarian hormones (follicle stimulating hormone and anti-mullerian hormone as the primary methods to assess ovarian reserve in clinical settings). The literature is inconsistent on the association between the FMR1 trinucleotide repeat length and infertility. Elevated levels of follicle stimulating hormone have been found in women who carry the premutation; however the literature on the relationship between anti-mullerian hormone and the CGG repeat length are too disparate in design to make a summary statement. This article considers the implications of two transgenic mouse models (FXPM 130R and YAC90R) for theories on pathogenesis related to ovarian endpoints. Given the current screening/testing recommendations for reproductive age females and the variability of screening protocols in clinics, future research is recommended on pretest and posttest genetic counseling needs. Future research is also needed on ovarian health measurements across a range of CGG repeat lengths in order to interpret FMR1 test results in reproductive age women; the inconsistencies in the literature make it quite challenging to advise women on their risks related to FMR1 repeat length.