Trisha is taking a break, champagne in hand, from her son Alexander's first birthday party.

As a woman of 43, with the womb condition endometriosis, this was a party that might easily have never taken place.

However, thanks to the skills of doctors at the Harley Street Fertility Centre - one of those with relatively low success rates in the latest figures - and perhaps a large slice of luck, her dream of a child has been realised.

She said: "That's why the figures are so unfair - these clinics often take much older women, or women whose health means they have a much lower chance of conceiving."

You have got to want a child so desperately to go through all this

It was only when Trisha, from Finchley in London, reached 37 that she realised that getting pregnant was not going to be a natural affair.

Her GP recommended a London-based private clinic, and she began a process now familiar to thousands of women in the UK.

Powerful ovary-stimulating drugs were followed by scans.

If these showed sufficient numbers of mature eggs, these would be harvested in a minor operation, and then hopefully fertilised by her partner's sperm.

No eggs

The resulting embryos would then be put back - and, in theory pregnancy could progress from there.

However, things did not run this smoothly.

Trisha's age, and probably her endometriosis meant that, despite the drugs, no suitable eggs matured.

She said: "The clinic told me that I would never have my own children, and recommended I use donated eggs.

If I won the lottery I'd spend it all helping couples to have IVF babies

"Obviously, that was very bad news for me."

After talking to friends, she decided to seek a second opinion, and went on to the Harley Street Fertility Centre.

She had another series of failed attempts to stimulate egg production, and then, at last, she became pregnant.

However, it is likely the embryo was defective in some way, as she suffered an early miscarriage.

Tragedy

She told BBC News Online: "Those were terrible times for us. I felt as if my world had ended.

"It's still something I find very difficult to talk about."

Many women might have given up at this point, but Trisha was determined that, having come so close, she should carry on.

"I told myself that I would be pregnant again by Christmas of that year - and I got myself fitter, because IVF is more likely to work if you are fitter."

The next cycle of treatment came, and she became pregnant again, in December 2000.

This time, it was no false dawn, and she gave birth to a boy in August last year.

"You have got to want a child so desperately to go through all this - it's no use saying: 'I fancy having a child', because you need to be determined, to go through everything you need to go through.

"IVF does work - that's the thing."

She estimates that she has spent in the region of �30,000, and is sympathetic to those who simply cannot afford those kind of fees.

"It's better for us - we're older, we've had our careers and made our money, but it's so different for young people.

"If I won the lottery I'd spend it all helping couples to have IVF babies."