Research presented at the annual conference of the American Society for Reproductive Medicine (ASRM) in New Orleans last week suggests that women who have children at an advanced age may pass fertility problems on to their daughters.
The researchers studied 74 women aged under 35 who were undergoing fertility treatment, asking them what the ages of their parents were when they were born, and what was the age at which their mother went through the menopause. The patients' husbands were asked similar questions. Of the group of women who succeeded in getting pregnant, the average age of the mothers was 25.7 years, compared with 28.2 years in women who did not get pregnant. Similarly, the average age of the fathers of the first group of women was 28.2 years, compared to 31.9 years in the second group. The average time span between the age at which the mothers gave birth to their daughters and their menopause was 24.7 years for the women in the first group, but this fell to almost 20 years for women in the second group. Altogether, the results showed that many of the women whose treatment was unsuccessful had themselves had older mothers. It also showed that the mothers of these women had experienced a shorter period of fertility after the birth of their children, before entering the menopause.
The researchers suggest that the reason for this might be the passing on of biological 'flaws' that make it more difficult for their daughters to become pregnant - this may have something to do with the age of the mothers' eggs at the time of conception, they surmise. They say that the findings suggest that older eggs may carry in-built defects related to fertility that only become apparent when the subsequent female offspring attempt to conceive themselves.
Dr Peter Nagy, from Atlanta-based fertility clinic Reproductive Biology Associates, was the lead researcher in the study and presented the findings to the ASRM conference. He said that the results could show that delaying childbirth has implications for women that could pass to the next generation. He pointed out it was well known that older women found it more difficult to conceive due to the age of their eggs (which are all present at birth), but that it had never been shown that this could also lead to subtle defects in the fertility of girls born as a result, making it harder for them to conceive as well. It may be that the decline in quality of a woman's eggs as she gets older could be passed on into the reproductive cells that eventually become her daughter's eggs, he suggested. 'For every year that a woman delays childbirth, it becomes more difficult for her daughters', he said, adding that women should think about 'whether their decision not only affects their own chances of getting pregnant but the chances for their daughters'.
Dr Nagy said that the preliminary results shown in his study would need to be followed up by looking at a larger sample of the general population, acknowledging that his own sample was both small and unrepresentative, being comprised only of women already having problems with their fertility. Bill Ledger, professor of obstetrics and gynaecology at the University of Sheffield in the UK said in response to the study that 'it needs to be looked at in more detail because more and more women are putting off having children until they're older and we know there are more risks to that such as the chance of having a baby with Down's syndrome', adding 'if she gets pregnant at 35 or 40 the eggs have been sitting in the ovaries for many years'. But, he pointed out, other, more subtle effects of delaying motherhood should also be taken into account.