Study: Do BRCA mutations affect fertility?

IN DEPTH REVIEW OF RESEARCH

Study background:

A woman is born with all of the eggs she will have throughout her life. Each month during her menstrual cycle, she releases one egg and in general, the healthier eggs are released when she is younger and the less healthy eggs are released later on. This is often referred to as lower ovarian reserve.  Healthier eggs have a higher chance of resulting in a pregnancy, making it more difficult for women to get pregnant at older ages.

Some studies have suggested that BRCA genes are involved in reproductive aging, while others have not. Kelly-Anne Phillips and colleagues at the Peter MacCallum Cancer Centre in Australia and colleagues published findings in the journal Human Reproduction where they looked at how BRCA status affected ovarian reserve (as measured by concentration of the hormone called AMH (Anti-Müllerian hormone) in the blood.

Researchers of this study wanted to know:

1. Does having a BRCA1 or BRCA2 mutation result in women having a lower ovarian reserve?

Population(s) looked at in the study:

The researchers used blood samples from 172 BRCA1 mutation carriers and 216 women from families with BRCA1 mutations who did not carry the mutation in their family, as well as 147 BRCA2 mutation carriers and 158 women from families with BRCA1 mutations who did not carry the mutation in their family. These women were between the ages of 25-45, had two intact ovaries and had no personal history of any cancer (except for non-melanoma skin cancer). Researchers measured AMH (Anti-Müllerian hormone) concentrations in the blood, which is a measurement of ovarian reserve as AMH is a hormone produced by eggs and represents a woman’s overall egg pool. AMH is a good measurement of ovarian reserve and is one of the most important tests that fertility specialists use when counseling patients.  

Study findings: 

1. On average, BRCA1 mutation carriers had lower ovarian reserve as measured by AMH concentrations than women who did not carry BRCA1 mutations.
   • The difference is comparable to a two-year increase, meaning a 35-year old woman who is a BRCA1 carrier and a 37-year old woman who is a non-carrier had similar ovarian reserves.
2. There was no difference between the average ovarian reserve as measured by AMH concentrations between women with BRCA2 mutations and women without BRCA2 mutations.

Limitations:

The sample size used in this research study was relatively small. While the researchers saw that there was no difference in AMH concentrations between BRCA2 carriers and non-carriers, this may be because there were not enough BRCA2 patients in the study for the researchers to see a difference.  

Conclusions:

While this study suggests an association between BRCA1 mutation status and a lower ovarian reserve, more work needs to be done to confirm this finding, in addition to the BRCA2 finding, as it was a relatively small study. Additionally, because the difference in AMH concentrations between BRCA1 mutation carriers and non-carriers was not large, the authors write “…it is possible that the findings of our study might not translate to clinically relevant fertility implications for younger women, but may be important for the subgroup of BRCA1 mutation carriers who wish to conceive in their late 30s or 40s when fertility is reduced even in the general population.” Young BRCA1 mutation carriers do not need to rush to have children based on these findings alone. However, women in their late 30s and 40s do already have a reduced ovarian reserve due to age—may want to talk to a fertility expert, particularly if they are having trouble conceiving. These experts may suggest trying to conceive at an earlier age or freezing their eggs.

Posted 5/23/16

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