Reduced ovarian reserve associated with increased risk of trisomic...(ieved during the fertility treatment; 3)...),Health

They found that a history of ovarian surgery increased the risks of trisomic pregnancy more than three-fold; if only four or fewer eggs were retrieved during treatment, this quadrupled the risk of trisomy (conventional IVF aims to retrieve between 8-10 eggs at one time); if there were signs of the menopause at the end of the study period, this increased the risk of a trisomic pregnancy more than five-fold.

"The biological mechanism behind our findings is, as yet, unclear," said Dr Haadsma. "It may be that women use their 'best' eggs first in their fertile life and leave their abnormal ones to the last. Women with fewer eggs would then be at increased risk of trisomic pregnancy. However, more convincing in my opinion, is the hypothesis that the chance that a fertilised, abnormal egg is selected for embryo transfer in IVF is increased in women with reduced ovarian reserve, simply because there are fewer eggs and thus embryos to choose from. The proportion of normal and abnormal embryos may be the same in women with normal and diminished ovarian reserve, but if you only have one or two embryos available (instead of, say, six or eight) the chance that no normal embryo is available is relatively high."

As women get older their supply of eggs decreases. In younger women, the reasons for a diminished ovarian reserve are more complex. "Next to ovarian surgery, other medical interventions, such as chemotherapy or radiotherapy, may cause a decrease in ovarian reserve. However, a woman's ovarian reserve is most likely to be mainly determined by her genes: the number of oocytes a woman is born with and the rate of depletion of her oocyte pool is believed to be heritable. This is reflected in the similar ages at menopause of mothers and daughters. However, exactly which genes are involved remains to be determined," said Dr Haadsma.

She concluded: "Since
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