Women with a gene mutation known to increase the risk of breast, ovarian, fallopian tube and peritoneum cancers are being advised to plan for babies earlier in case they run out of eggs.
The warning comes after a new international study discovered that woman with a certain cancer gene have lower egg counts than other women their age.
The study, led by Peter MacCallum Cancer Centre oncologist and National Breast Cancer Foundation fellow Professor Kelly-Anne Phillips, checked the levels of anti-Müllerian hormone (AMH), which is an indicator of egg count in the ovaries.
Women with the BRCA1 mutation were found to have a 25 per cent lower egg count than women of the same age without the gene.
“This means that women in their mid-30s who carry the BRCA1 mutation have, on average, ovarian reserves similar to those of non-carriers who are two years older,” says Professor Phillips.
Through a woman’s lifetime, AMH levels decline in line with the number of eggs remaining in her ovaries.
But Professor Phillips says AMH is only one indicator of potential fertility. She says women with low AMH levels can sometimes still have a baby while women with high AMH levels are sometimes unable to do so.
“However, our findings suggest that women carrying the BRCA1 mutation who wish to have children should avoid, where possible, delaying pregnancy until their late 30s or 40s when fertility is reduced anyway because of their age,” she says.
“For women trying to conceive in their 20s, any difference in ovarian reserve between BRCA1 mutation carriers and non-carriers is unlikely to be of clinical significance.”
However, such genetic mutations are rare in the general population – about 0.1 per cent of people have the BRCA1 mutation and around 0.2 per cent have the BRCA2 mutation.
The study, published in the scientific journal Human Reproduction, analysed AMH levels from almost 700 women aged 25-45. The researchers adjusted their analysis to take account of age, oral contraceptive use, body mass index and smoking.
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