Thirty weeks into her first pregnancy, Jenny Chambers' limbs began to itch. She was told not to worry: at that time doctors and consultants were taught that itching during pregnancy was unimportant. But shortly before she was due to give birth, her daughter, Victoria, died in the womb. It was classed as an "unexplained still birth". These things happen, she was told, and it wouldn't happen next time.

In 1988, pregnant for the second time, the itching began at 28 weeks. This time Chambers broke her kneecap in a fall and was admitted to hospital. Confined to her bed and constantly monitored, her baby was induced at 38 weeks. The little boy, Alex, was fine.

In 1990 she was pregnant again with her daughter Olivia, and this time she became unbearably itchy after 27 weeks - hands, feet, arms, legs - "an army of ants was marching under my skin". She couldn't sleep. She scratched until she bled.

Convinced there must be a link between the itching and the loss of the first baby, she and her husband begged the hospital to induce this one by 38 weeks, but they were repeatedly told they were worrying unnecessarily. "No one was listening," Chambers says. Eventually, the doctors announced they would induce her at 39 weeks.

Two days before the date set a hand-held heart monitor showed the baby - little Olivia - alive and well. Yet within six hours the baby was dead. After a short labour, Jenny held her in her arms. "What amazed me was, she was so warm. So perfect. I didn't want to give her away. I wanted to get off the bed and run out of the hospital with her."

The maternity unit called it another unexplained still birth, but Chambers was certain there was an explanation. A senior registrar suggested she talk to a different obstetrician called Judith Weaver in the same hospital. Chambers went to see her and asked: "Do you know why my babies died?" Weaver replied: "Yes. I know exactly why they died."

Weaver told her about obstetric cholestastis, an under-reported and under-diagnosed condition of pregnancy which for some reason can cause stillbirth in pregnancies. Weaver explained that certain blood tests Jenny had during pregnancy had showed a disorder of her liver function - her bile production wasn't flowing normally, and bile had built up in her blood. This hadn't been picked up because her doctors had been taught it didn't matter as she wasn't jaundiced. But what they'd been taught was wrong. Weaver told Jenny that if her baby had been delivered by 38 weeks, "she would have been alive today".

Grieving and shocked, Jenny and her husband considered suing the hospital. But instead they "decided it was better to make sure it never happened again, to anyone else". She threw herself into researching the disease. A friend - a GP who, like most, had never heard of obstetric cholestasis - downloaded articles from the internet. It was clear that if a woman itched in pregnancy, and her liver function tests proved abnormal, the chances were that she had OC, and the solution was simple - delivery by 37 or 38 weeks could prevent nearly every still birth caused by the disease.

Chambers realised that just because a few top doctors had heard of the condition, it didn't mean the message had got into the system. So she began her intensive campaign to raise the OC profile. Through the helpline she set up, she met other women who had lost babies, and encouraged them to join her fight to spread the word.

She never went back to her building society job. Instead she became a phlebotomist - someone trained to take blood - as a way into the NHS. Once inside the system, she spoke to people in labs working in clinical chemistry. She linked up with doctors who were starting research projects in Birmingham and London, and travelled the country lecturing to members of the medical profession.

She sat on the board of a government inquiry into perinatal mortality and, at her insistence, the board included checks for liver function and bile acid in its battery of tests. Results showed that nearly 5% of unexplained still births were probably related to OC. This meant one baby a week in Britain was dying an easily preventable death.

It was solely down to Jenny Chambers that during my latest pregnancy I reported itching to my consultant at Whipps Cross hospital in London. None of the (up-to-date) pregnancy books I'd bought mentioned OC in the index, but I'd read one of the paragraphs Chambers had placed in a baby magazine, and also the entry in the NHS pregnancy guide. My consultant referred me to a colleague, Catherine Nelson-Piercy, who diagnosed OC, a condition currently being researched at Whipps Cross. I was monitored daily, and induced just before 37 weeks. (Twins Imogen and Seán are doing well).

I was amazed how much respect Chambers, a lay person, had among medical professionals. Nelson-Piercy refers to her as her "very good friend" and credits her with the fact that a lot more people know about the disease now than did eight years ago. Andrew Shennan, a senior lecturer at St Thomas's hospital in London, who leads London-based research into the prevalence of OC, also considers Chambers to be "hugely instrumental" in raising understanding of the condition. He refers to her single-handed campaign as "unique".

Current studies are far from complete. The prevalence research only began last August and relies for funding on the perinatal charity Tommy's Campaign. No one is yet sure how many pregnant women get OC (the guess is around 1% to 2% in this country), or how many of those pregnancies are likely to end in still birth if they go to term (possibly 2%). Nobody yet knows why there is a connection between OC and still birth - only that the connection exists. It is very much the case that most women who itch in pregnancy will suffer no ill effects. But there is no need to take chances, because the diagnosis is simple, as is the solution.

Thanks to Chambers, most hospital consultants today are aware that itching is not necessarily benign and will investigate further. Nelson-Piercy agrees, however, that many GPs and midwives are still behind the times. Her message for pregnant women is: "If you itch, don't just request a medical opinion - ask firmly to be given a liver function test."

As for Jenny Chambers, after Olivia's death she vowed never to try for another child. But later, with Weaver as her consultant, she went on to have another son. Baby Tim was induced for everyone's peace of mind at 35 weeks, after another horribly itchy OC pregnancy.

Now 42 years old, Chambers is sad she's never had another daughter, but she cannot regret the two she had. "My work can't bring back my girls," she says, "but it can make sure they didn't die in vain. I feel their deaths have achieved so much."

For more information, call the Obstetric Cholestasis Support Group on: 0121-353 0699