Parenting: Louise Holden reports on 'geriatric mothers' - the fastest- growing group in our maternity hospitals

Actress Courtney Cox Arquette is finally pregnant and at 39 years of age, she is part of a growing cohort of what obstetricians once described as "geriatric" mothers.

There has been a significant shift towards a later childbearing age here over the last 40 years. The predominant childbearing age has moved from 25-29 years to 30-34 years. Last year, in the National Maternity Hospital in Holles Street, Dublin, 29 per cent of all births were to women between the ages of 35 and 39, up from 14 per cent a decade ago.

Despite this development, women having babies in their mid to late 30s - and later - can find themselves treated like the exception rather than the rule. Jan Anderson, who authored a book on the subject, describes her experience on discovering that she had become pregnant at the age of 40.

"I immediately scoured the Internet for articles and statistics on pregnancy over 40, since that was the age I would be at the time of the birth.

"What I discovered set me into a state of premature panic. Terms such as chromosomal defects, fetal abnormalities, miscarriage, diabetes, placental abruption, pre-eclampsia, placenta previa, prolapse (of everything) and stillbirth leaped off the page. The consensus of medical opinion seemed to be that I was completely past it and was taking a huge risk even considering pregnancy at my pre-pensionable age."

There's no doubt that the older the woman, the greater risks pregnancy carries. A woman is born with all her ova at birth and they age with her. The older the eggs, the more likely that they will carry chromosomal abnormalities. For this reason, the demand for screening services is on the increase.

However, the odds of a woman over 35 having a healthy pregnancy and normal labour are overwhelmingly favourable. As in all age groups, the health of the mother is a far better indicator of outcome than age. It has been suggested that the higher rate of intervention recorded for older mothers may be as a result of perceived, rather than actual risk.

An audit carried out by the Royal College of Obstetricians and Gynaecologists, published in 2001, found that, while older women were more likely to have complications in their pregnancy, this is probably not the only reason why they have more Caesareans - their own or their consultant's preference also played a part.

Another analysis, detailed in the British Medical Journal, looked at 23,806 births between 1988 and 1997, details of which were taken from the Aberdeen Maternal and Neonatal Databank in Scotland. The ratio of Caesarean to natural delivery births for women over 30 was compared to that for those in their 20s. Scientists found that women aged 30 and 31 were twice as likely to have an emergency operation than those under 30. Women over 40 who were already mothers were three times as likely. Women of 38 or over were three to four times more likely to have a Caesarean than women in their 20s.

However, the study concluded that higher Caesarean rates among older women could not be explained by their increased risk of medical complications. The rise in the Caesarean rate outstripped the increase in the risk of medical complications, analysts found.

Jacqueline Bell from Aberdeen Maternity Hospital, who led the research team, commented: "People have suggested that obstetricians have a lower threshold of intervention in older women, and that older women themselves prefer Caesareans."

Family Therapist Gayle Peterson says that many women are surprised to find that the risks associated with later pregnancy are often overstated.

"Though there is a higher rate of complication in labour, including a greater number of Caesarean sections for older women, statistics do not separate out women who are healthy during their pregnancies from women who experience other medical problems, such as diabetes and toxemia.

"Most authorities on this topic agree that if you are generally healthy, get exercise and maintain a healthy diet, your chances of having a normal labour should not be any different now than when you were 25."

Declan Keane, Master of the National Maternity Hospital, agrees. "Maternal age should not dictate pregnancy and labour management. A fit and healthy 35-year-old is likely to have a far easier time than an unhealthy woman in her 20s."

What's new in the world of parenting

A blood test for a natural body chemical may be able to predict whether a woman has a high risk of miscarriage. Researchers in Australia found that, even weeks before losing their baby, women had reduced levels of a protein called MIC 1. The researchers are not jumping to conclusions about the finding, saying that bigger studies are needed.