The first study to investigate the parenting experiences of older IVF mothers has revealed that they cope equally well with the stress of motherhood as those who have children in their thirties and forties, and are no more likely to suffer physical or psychological ill health.

The findings come only a week after Lord Harries of Pentregarth, who chairs the Government’s fertility watchdog, argued that maternal age should not be a sufficient reason to refuse IVF treatment, and provide the best evidence yet in support of his case.

In an interview with The Times last weekend, the former Bishop of Oxford rejected calls for a strict upper-age limit, saying that he respected the decisions of women such as Patricia Rashbrook, who had a son at the age of 62 this year after travelling abroad for therapy. Doctors should instead be left to choose patients according to their own clinical judgment.

While there is no absolute age limit for IVF in Britain, the NHS will not fund it for women aged over 40, and it is difficult in practice for those aged over 45 to find even private clinics that are willing to treat them. Though use of eggs from young donors can cut the risk of genetic defects, which is higher for older natural mothers, low success rates and laws requiring doctors to consider the welfare of IVF children still lead most fertility units to reject older women as patients. Only 24 women over 50 had IVF births in 2002, the last year for which figures are available.

Numbers are also kept low because these patients generally need donated eggs to conceive, but the number of older mothers is expected to grow significantly in the future. New technology now allows women in their twenties or thirties to preserve their fertility by freezing eggs, which could be implanted in their fifties with a good chance of success.

Controversy surrounding the issue of older mothers centres on the likely impact on their physical and mental health, and that of their children.

Older women, particularly those over 55, have a higher risk of pregnancy complications such as pre-eclampsia, and many people question their capacity to care for their children as they grow old themselves. Dr Rashbrook, for example, will be 80 when her son turns 18.

The new research from the University of Southern California (USC), indicates that at least some of these concerns are misplaced. “There is reason to say, in the absence of other data, that maybe we shouldn’t jump to the conclusion that it’s wrong for women to become mothers at this age,” said Anne Steiner, who conducted the work with Richard Paulson.

In the study, which will be presented tomorrow at the American Society for Reproductive Medicine conference in New Orleans. The researchers investigated 49 women who had given birth at 50 or over between 1992 and 2004, after treatment with donated eggs at the USC clinic.

Each was matched with an IVF mother in her thirties and another in her forties, and all were sent questionnaires about physical and mental functioning and parenting stress.

The results showed no significant differences between the three groups on any of these measures. If anything, the oldest mothers suffered slightly fewer psychological problems than younger ones.

Dr Steiner, who has since moved to the University of North Carolina, cautioned that as the oldest children in the study were 13 when it began it was not possible to draw conclusions about parenting of teenagers. Even so, she said it supports Lord Harries’s view.

“The conclusion from this study, though it is limited and of a small size, is that, if we look from the perspective of stress and physical and mental functioning, it doesn’t seem like we can restrict parenting based on these reasons.” She also pointed out that older women in the study tended to have younger partners, and that this may influence their ability to cope.

Dr Paulson said opposition to older mothers rests not on evidence that they make poor parents, but on prejudice.

“Society still has these feelings about motherhood. The way we view the mother is much more circumscribed than for the father: she should be young and attractive. That is underneath all this talk about the ethics and legality of treating older women. Deep down, society has a fixed idea of what motherhood should be, and this causes deep discomfort.”

Bill Ledger, of the University of Sheffield, said that while the research was welcome it did not address all his reservations about giving IVF to women in their fifties. “It does not surprise me that they cope well with young children while they’re in their fifties, but what no one has looked at yet is what happens when these children are 18. It worries me that their parents will be in their seventies and eighties. I have yet to be convinced that a child will have a good quality of life if its parents are older than its friends’ grandparents.”

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