When my 11-year-old daughter came to me worried that she had breast cancer, I was horrified. She had read about the disease, we had often talked about it , and so she had decided that the tiny swellings beneath her nipples were malignant lumps. It hadn’t occurred to her that these bee-stings, as we called them when I was young, were the painful beginnings of breasts - her portal into puberty. The trouble is that while we might idealise childhood we don’t want to see our children entering puberty with its associations of spotty, unruly youths, lost innocence, the onset of menstruation and the spectre of teenage pregnancy.

However much we like to think we are more open than our parents were, talking to our children about the changes that take place in their bodies is still something many of us put off until too late.

Simon Blake, director of the Sex Education Forum at The National Children’s Bureau, says: “One in ten girls start their periods without any information at all. We still live in a culture that says that giving young children sex education is confusing. To me it’s storks and gooseberry bushes that are confusing.”

Part of the problem is in the title “sex education”. When I was young, the subject was not tackled until secondary school, well after many of the girls had reached puberty. Early developers were ostracised, thought to have entered some unnatural secret society that involved whispering, bloody knickers and sitting out of swimming.

Hattie, 11, says: “I hate the thought of starting my periods, having to sit out of swimming and all that stuff. On the other hand, I like the idea of growing up, and entering another stage of life.”

Rosie, 11, adds: “You read about 12-year-olds who have babies, it’s really scary. They can’t go to college or anything. I don’t think it’s cool to have sex.”

There is now increasing pressure to start the process of straightfoward sex education at six, seven and eight because it seems children are reaching puberty earlier. Many girls are confronted by breast-buds and hints of pubic hair at about ten, with the onset of menstruation at 12.

For some it is even earlier. A recent study by The Institute of Child Health claimed that the number of girls entering puberty at eight was as high as one in six.

While this was not a national study, most specialists would admit to a general trend. Yet guidelines on puberty are still based on a survey of fewer than 200 girls from a single children’s home in the 1960s.

“More children are coming to us for treatment for early puberty,” says Dr Jeremy Kirk, consultant endocrinologist at Birmingham Children’s Hospital. “It seems to have been a trend over the past 150 years, probably due to better nutrition.”

And if this is the case, our primary schools need to be much better prepared. According to a study released this week by the Child Health Department in Bath, primary school children needing sanitary towels had to ask a teacher, as only 1 per cent of schools provide dispensing machines. Nor were sanitary disposal facilities adequate.

Vivien Iviris was told that her 18-month-old daughter Lucy just had “puppy fat” when she began to develop breasts. “But by the age of two and a half, Lucy was bad-tempered and had spots and lank hair. She grew five centimetres in six months. It was like living with a bolshy teenager, at the age of two.”

Referred to a specialist, Lucy was diagnosed with a hamartoma, a benign brain tumour that triggered the hormones that induce puberty. Now, at nearly five, she is on treatment to halt the process.

“She has missed out on toddlerhood,” said her mother. “She looks like a mini-woman, with breasts and a little waist. She uses deodorant because she has body odour. She calls it her polish.”

Susan Saunders was fobbed off when her daughter, Chloe, showed signs of underarm hair and breasts at the age of four. Her height was that of a child three years older.

“I tried to kid myself that everything was OK,” says Saunders. “But then at a Christmas party, just before she was six, she started bleeding. She was very frightened.”

The Child Growth Foundation put her in touch with an endocrinologist who suggested monthly injections to halt puberty until she was ten.

“Her early relationships suffered. She was picked on, teased and talked about because she was so developed,” said her mother. “I tried to dress her in clothes that played it down and she tended to befriend taller, more developed girls like herself.”

Chloe, now 15 and 5ft 4in, seems to have suffered no ill-effects.

“These children may be physically mature, but they are not emotionally able to cope with it,” says Vreli Fry from the Child Health Foundation. “GPs need to be made more aware of the problems of early puberty, but health education shouldn’t be a big deal. It’s a wonderful thing that is happening; why does it have to be top secret?”

• Some names have been changed
• The Child Growth Foundation (020-8995 0257)
• Sex Education Forum at The National Children’s Bureau: www.ncb.org.uk/sexed.htm