Fragile X Syndrome and fertility
Genetic causes of premature ovarian failure and poor ovarian response
How can we help you?
Poor ovarian reserve can have a genetic basis and a fragile X syndrome genetic analysis can provide us with the answer.
What is fragile X syndrome?
Fragile X syndrome is one of the most common causes of a hereditary intellectual disability.
The gene that is responsible for the disorder is called FMR1 and it is present in the X sex chromosome (it is a gender-related disorder). As a rule, we say that men suffer from it whilst women transmit it. As indicated below, there is a repeat region in the FMR1 gene (expansion) and its size determines whether or not an individual has the disorder or not.
What is the link between fertility and the FMR1 gene?
There is a length range in the FMR1 gene repeat region called premutation. In women, it causes an increase in the risk of having disorders that range from poor ovarian reserve to premature menopause. Around 20% of women with premutation suffer from premature ovarian failure in comparison with 1% in the rest of the population.
What does a fragile X syndrome analysis consist of?
In a genetic analysis, we determine the length of the repeat region in the FRM1 gene.
There are three main ranges in terms of the number of repetitions:
- Between 5 and 55 repeats. In this range, individuals are normal.
- Over 200 repeats (full mutation) means that the individual has the disorder. Children with a full mutation have certain specific clinical characteristics as well as mental retardation. It is less severe in girls that have a full mutation of the phenotype and their mental retardation can be simply borderline intellectual functioning.
- There is an additional third possibility (premutation) that is characterised by between 55 and 200 repeats. These patients do not have any of the disorders’ symptoms but they can pass it on to the next generation since there is a chance of the number of repetitions being greater in offspring. Furthermore, these women have an increased chance of having fertility issues linked to ovarian reserve.
When is a genetic analysis advisable?
An analysis of the number of repeats in the FMR1 gene is recommended in patients with poor ovarian reserve or premature menopause. Should premutation be identified, appropriate genetic guidance must be given because of the increased risk of having a child with fragile X syndrome. In these cases, couples must be given guidance so that they can choose freely whilst also understanding the risk they are undertaking and being fully aware of the therapeutic options that are available to them: prenatal diagnosis, PGD and egg donation.