A woman's potential fertility can be predicted from the age her mother went through the menopause, a study has shown.
Ovarian reserve - the number of eggs a woman has left in her ovaries - was found to decline faster in women whose mothers had an early menopause.
The findings suggest that a woman's fertility is, to some extent, inherited from her mother.
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Earlier statistical studies had already indicated the trend, but the new research confirmed it by looking at two physical markers of ovarian reserve.
Scientists measured anti-Mullerian hormone (AMH) levels and antral follicle count (AFC) in daughters and compared both with mothers' age at menopause.
Both markers reduced at a faster rate in daughters of mothers who had the menopause early.
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Study leader Dr Janne Bentzen, from Copenhagen University Hospital in Denmark, said: "This is the first study to suggest that the age-related decline of AMH and AFC may differ between those whose mothers entered menopause before the age of 45 years and those whose mothers entered menopause after the age of 55 years.
"Our findings support the idea that the ovarian reserve is influenced by hereditary factors. However, long-term follow-up studies are required. Conclusive evidence can only be obtained when we have longitudinal studies that follow women who have AMH measurements over time until menopause. Therefore, interpretations of our data are limited and the findings we have described may not occur in any given individual."
The results are reported in the latest online edition of the journal Human Reproduction.
A total of 527 women aged 20 to 40 working in health care at Copenhagen University Hospital took part in the research.
They were divided into those whose mothers had an early menopause up to the age of 45, those whose mothers had a normal menopause between the ages of 46 and 54, and those whose mothers had a late menopause at 55 and older.
Average AMH levels declined by 8.6%, 6.8%, and 4.2% per year in women with mothers who had early, normal or late menopauses respectively.
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A similar pattern was seen for AFC, with annual declines of 5.8%, 4.7% and 3.2% per year in the same groups.
AMH levels and AFC were also significantly lower in contraceptive pill users compared with non-users.
AFC was lowered by an average 11% in women whose mothers smoked while they were pregnant.
Dr Bentzen said the effect of oral contraceptive use was probably temporary and unlikely to influence ovarian reserve in the long term.
However she added: "We believe there is a need for longitudinal, large studies in which ovarian reserve parameters are measured repeatedly in the same individual before, during and after the use of oral contraceptives. Additionally, we need to explore the impact of dose-response and duration of hormonal contraception on markers of ovarian reserve."
In their paper, the researchers wrote: "From a biological point of view, it may be reasonable to assume that a low ovarian reserve may have a long-term effect that will shorten the reproductive lifespan. We therefore assume that markers such as 'maternal age at menopause' in combination with AMH or AFC, and chronological age, may represent a more complete picture when evaluating the ovarian reserve of the individual."