Esme Atiya-Alla was 51 when she adopted two-year-old Georgina. In the two years since then, there have been times at the shops with her daughter, when people have bent down and asked, 'Where's your mum?' Her reply of, 'Here,' has often been met by a startled look - followed by a smile.

Despite the stigma society attaches to older mothers, Atiya-Alla insists that becoming a mother again in her fifties has been a wonderful experience.

Georgina, she says, is an 'endearing, beautiful young girl'. Like lots of the friends she has been making at her new school, the four-year-old loves Scooby-Doo, plays with Barbie dolls and can be a live wire. The fact that her mum is 49 years older than her has rarely been an issue: 'Most people have been supportive,' says Atiya-Alla. 'I don't stand out too much in the playground because there are lots of grandparents and I don't think people care that much if I'm her mother or her grandmother'.

Atiya-Alla had already adopted Georgina's older sister, Clare, and was delighted the siblings could be together.

The 53-year-old strives to keep fit so that she can keep up with her children. She goes to the gym regularly and swims with her daughters. Having young children, she says, has helped her to feel younger and stay in touch with fashion. And there is no sign that Georgina has suffered.

Atiya-Alla is not alone. She is part of a growing trend of mothers who adopt and give birth later in life and enjoy the experience. For women over 40, pregnancy rates rose by 41 per cent through the 1990s and into the new century and by 27 per cent for those aged between 35 and 39. Over the same period the rates for those under 30 fell by nearly 15 per cent.

The trend is highlighted among celebrities. Lynda La Plante, the crime writer, recently adopted a child at 57. She had tried for years to have children and eventually started fertility treatment. But two years later she was told she had started the menopause and could not conceive.

She secretly adopted a sixth-month-old baby boy in America: 'I've had every kind of IVF there is. But everything failed. My fantasy was always to have four beautiful blonde children. It's very frightening to reach a point in your life where you think: "If I die tomorrow, where does this go?"

Her son is called Lorcan, and she describes him as 'a miracle, an absolute joy, my gift from God'.

Photographer Annie Leibovitz successfully conceived using a sperm bank and went on to give birth to Sarah Margaret, who is now two. She admits that she finds parenting exhausting and sometimes wishes she was 'a little younger and had more energy'. But she also describes motherhood as 'just incredible'.

Leibovitz and La Plante add to a string of others: Geena Davis gave birth at 46, Madonna had baby Rocco when she was 42, Cherie Blair had Leo aged 45 and Sarah Jessica Parker gave birth at 37.

Like La Plante and Atiya-Alla, many women who adopt prefer to do it later on in life. In 1999 the average age of single adopters was 40 years and four months. The average age gap between the adopter and the child was 35 years and seven months, with the biggest gap being 54 years, according to statistics from the British Association for Adoption and Fostering.

The ages of mothers at childbirth has also risen dramatically. In 2002 there were just under nine births per 1,000 women aged 40. This has nearly doubled since the 1980s. The average age for women to have children has risen to 29.3 and the average number of children a woman will have is 1.65, half the amount of the 1960s.

Almost one in five women now has no children and the fastest growing age-group for births is women aged 35-39 and 40 and over. The cause of the trend has been widely debated. It could be a generation of determined career women unwilling to take time out earlier in life, or medical advancements that can help support later births.

But while many have highlighted the health risks and social stigma that can result, more and more experts are now pointing out the potential benefits.

In a study by the University of Leicester that looked into how well young children were doing educationally, those with older mothers scored significantly better than those with younger mums.

The study, 'Motherhood after 35: mothers and four-year-olds' showed a positive correlation with mothers' age, partners' age, learning stimulation in the home and age last breastfed.

'In several respects, children of older mothers seem to gain,' says leading expert Dr Julia Berryman, who co-authored the study. 'For example in breastfeeding, parental responsiveness and discipline styles. One finding of particular interest is the better performance on ability tests by children of older mothers'.

Berryman showed that older mums often planned their pregnancies, and were more likely to have suffered a miscarriage in the past. They also had longer second stages of pregnancy and gave birth to heavier babies. But in terms of well-being during and after the pregnancy 'age tended to be relatively unimportant'.

For many mothers, trying and failing to have children can be a long and painful experience. Adoption becomes an increasingly attractive solution as the possibility of having their own children diminishes. Providing a home for a baby who needs it can be incredibly fulfilling.

Vimel Aggarwal, a GP from Greater Manchester, gave birth to Sangeeta when she was 39 and then adopted Kavita as a baby when she was 45. Aggarwal says that having an 11-year-old in her fifties 'keeps me young'.

Aggarwal has accompanied her daughters to concerts to see S Club 7, Steps, the Spice Girls twice and this year, aged 56, to Christina Aguilera. She takes them swimming every Sunday and regularly takes them to the cinema. This weekend she hosted a sleep-over.

'All our close friends were supportive,' says Aggarwal. 'We were worried, not about her as a young child but whether we would be too old when she reaches university to support her. I still worry a bit but she is doing really well.'

Kavita is a boisterous 11-year-old who has lots of friends and is doing well in school. Sometimes she says, 'I have the oldest mum in class,' but on the whole they have a healthy, happy relationship that benefits both mother and child.

There many be a great number of advantages that society doesn't think about, but the medical risks for late-in-life births are well-known.

The miscarriage rate for the over-40s stands at 40 per cent and the chances of a child being born with Down's syndrome increases.

Berryman accepts these risks but emphasises that age is not the only factor that may affect the health of mother and baby: 'Some birth complications have been linked to maternal age, but there is no simple relationship and many factors appear to play a role'.

She also suggests that 'the slightly increased medical risks of later child bearing are offset by the advantages in children's cognitive development.

Others points out that pregnancy also offers a degree of protection to the mother from diseases such as breast cancer.

Professor Ian Craft from the London Fertility Centre has helped many mothers give birth in their late fifties.

'Everyone who wants a child has the right to seek advice and we are obliged to take every case seriously,' he says. 'All our patients have to go through counselling and careful medical screening before they can be accepted for treatment'.

Older women who come to him for help 'haven't done it flippantly', he says. 'The choice has been made after great consideration. And why shouldn't they be happy?'

Experts who want to help mothers at a later age do so knowing that it could bring great happiness to families desperate to have children. They are not suggesting that women should strive to give birth later but point out that the stigma attached to it is often unfounded.

'It would be wrong to conclude that there is a right time for motherhood,' says Berryman.

'Becoming a parent is a decision that has to be made in the light of many factors, of which age is only one.'