Focus Part Two: The couple - Kylie wanted a baby. The clinic wanted eggs. They made a deal. If only life were so simple...

Kylie and Aaron Sidney vow never to go down the baby- technology road again. Not only have they failed to have a child but Kylie has also endured two miscarriages, over-stimulated ovaries, a suspected pulmonary embolism and a severe allergic reaction to the drugs. "I walked into the fertility clinic a fit, fertile woman, full of hope; three years later, aged 25, I've come out an infertile woman with nothing but regret and bad memories," she says.

Aaron and Kylie couldn't have children because he had had a vasectomy in his first marriage. They met in 1997; she already had two children and he had three, but they were desperate to have a baby together. Despite the severe emotional pressure of fertility treatment, theirs is a strong marriage. From the age of 17 she wanted nothing more than to have children; he, 11 years her senior, is a protective man who has embraced her two children as if they were his.

Because they couldn't afford Aaron's vasectomy reversal, Kylie came up with the controversial solution of trading her eggs in part-exchange for the operation. But having contacted a number of clinics, she was turned down on medical grounds, on account of having had two miscarriages.

Only one clinic responded positively - the London Fertility Centre, run by the pioneering infertility expert Professor Ian Craft, who invited the Sidneys to his Harley Street office. Professor Craft uses a similar system as egg-sharing, called egg-giving. But rather than two women sharing one harvest of eggs, the woman providing eggs gives one month's harvest away and then uses a second harvest for her treatment. In this way, there are more eggs and more chances of getting pregnant.

Professor Craft says that there is a small risk involved, but one that is no different from the risks of fertility treatment.

"A scan showed I had mild PCO [polycystic ovarian syndrome]," says Kylie, "but they said it wouldn't affect the treatment." The treatment made her feel odd even before the egg collection.

"My whole body was bloated. My face was a big, fat moon. I even had to go to the jeweller's to have my wedding ring cut off," she says.

Then came the operation to collect eggs. "Coming to, it felt like a huge piece of concrete had been dropped on my chest. I was vomiting and screaming. They said that I was hyperstimulating."

At home in King's Lynn, Kylie was unable to get out of bed and Aaron called an ambulance. In hospital, she was given oxygen and put on a drip. Her condition had been exacerbated, it transpired, by Voltrol - a painkiller which had caused an allergic reaction.

Despite her poor health, Kylie was determined to go ahead with the second egg harvest three months later. "My mother was dead against it," she says, "but I wanted a child and I was going to get one."

This time, when she woke from the egg-collection operation, the pain was crushing, she could barely breathe and she had to be dressed by two nurses and helped to a taxiby Aaron (himself recovering from the operation to collect sperm). Before she went she was given a paracetomol-based drug, despite claiming to have warned the clinic she was allergic to it. "At King's Cross the guards wouldn't let me on the train at first - they thought I was drunk because I was vomiting, crying and could barely walk."

The next day Kylie collapsed on the sitting-room floor. "She went blue and her eyes were bulging. I tried to resuscitate her but was sure she was a goner," says Aaron.

The cause of her problems again seemed to be hyperstimulation. In tonight's Panorama on BBC1, Professor Craft stresses that hyperstimulation is a routine part of all fertility treatment, and that patients sign a consent form that tells them this.

Kylie and Aaron decided yet again to try for a baby and went ahead with another embryo transfer. Following the operation, she was assured by the clinic that it had been an easy transfer. A home pregnancy kit test was positive but after days of uncertainty she was informed she was having a miscarriage.

She sank into a depression, unable to look after the children or carry on working as an agency nurse. "Aaron tried to be sympathetic but I didn't want his sympathy. I wanted his congratulations."

In February 2002, there was another embryo transfer. The Sidneys' hopes were once again raised only to be dashed - two weeks later Kylie miscarried. Following a small service with the chaplain of the King's Lynn hospital for all her failed embryos, she returned home and collapsed, determined never again to go through the ordeal of fertility treatment.

The couple were offered another free-of-charge embryo transfer, but it had to be stopped early because the combination pill Kylie was given resulted in deep vein thrombosis.

Despite all this, the Sidneys haven't given up. While never stopping grieving for their "tiny unfinished babies" they still hope to have a baby some day. Three weeks ago Aaron's company loaned him the money for a vasectomy reversal and Kylie is hoping that one day through surrogacy, using Aaron's sperm, she will get the baby she longs for.

Now, snuggling up to her husband, Kylie says, "Financially I have sort of wrecked the family because it meant that I couldn't hold down a job."

Even though at times her obsession with having a third child nearly wrecked their marriage, Aaron has stood by her, accompanying her to every appointment and claiming to want a baby as much as she does. "But it was a nightmare," he admits. "Kylie was totally preoccupied."

Aaron and Kylie Sidney tell their story tonight on 'Panorama', BBC1, 10.15pm