When Persona, the first technological piece of contraception, burst on to the market in October 1996, it seemed a godsend to Mandy Mayes, a mother of five-year-old twins. Then 33, she had tried every form of birth control, but none of them had really suited her: the pill gave her headaches and a pain in her arm; the coil made her haemorrhage; and her husband just plain didn't like using condoms.
And so she was more than willing to embrace a method that appeared as natural as possible. "I thought it was the answer to all my problems," says Mayes, now 38, a receptionist from Ipswich, Suffolk. "It implied it was really reliable. I knew the success rate was 94% but that is the same rate as the coil and I'd never got pregnant on that. I had tried everything else and this seemed safe."
Just over a year after using Persona, however, she discovered she was pregnant. Her world turned upside down. The twins had just started school and she had resumed her career in charge of reception at an NHS trust, but all that changed with the birth of Georgia, now three.
"I was angry and felt totally cheated - of my career and my ability to choose if and when I had children," she says. Becoming pregnant also had a dramatic effect on the family: "Without my salary, we had huge money worries and couldn't do things like go on holiday; I got sterilised because I felt I couldn't trust any contraception; and I became depressed because of this and the loss of my job. It put an enormous strain on my marriage. We separated 10 months ago and this had a lot to do with it."
While Mandy's experience may seem exceptionally unlucky, it is far from unique. Promoted as "the biggest thing to happen to contraception since the 1960s", and approved by the Vatican, Persona soon had Marie Stopes International estimating that an extra 60 women a month were seeking abortions, and led the deputy chief medical officer to warn women not to use it if becoming pregnant would be "unacceptable".
Now 65 women who did become pregnant are suing Unipath for breach of contract, misrepresentation, negligence and having produced a defective product under the 1987 Consumer Protection Act, in an action that could cost the multinational company £9.7m. Unipath, which has said it will robustly defend the action, is expected to argue that these pregnancies were a result of user error: in short, the women took risks with or misused the technology.
But the women, who were prepared to shell out £49.95 for the initial starter kit and £9.95 a month thereafter, will argue that the fault lies with the device itself and in the fact that the product was launched on the back of research that made a number of questionable assumptions. "My clients are highly articulate, well-educated women who were very assiduous in the way they used this device," says Alison Williams, a clinical negligence specialist at Plymouth-based Wolferstans solicitors who is representing 10 of those in the action. "There are a number of lines we will be pursuing, but basically, we will be arguing that this research was flawed."
To understand their arguments, you need to look at how Persona works. A neat, hand-held computerised monitor, it acts on the same principles as the rhythm method by predicting when a woman is in the fertile or infertile part of her cycle. It does this by measuring changes in the concentrations of lutenising and E3G hormone in a woman's early-morning urine - hormones which indicate when she is receptive to sperm or close to ovulation - and, using statistics programmed into the computer, then indicates if she is likely to get pregnant. A green light flashes if it is safe to have sex, a yellow one, requiring a urine test, if there is any doubt, and a red one if unprotected sex is a no-go. Used correctly, Persona purports to be 94% reliable with just six women a year, or one in 17, becoming pregnant due to the machine incorrectly identifying their fertile days.
The women are set to argue, however, that Persona is based on a number of "unproven" and "uncertain" assumptions, including the belief that it is reliable for female cycles of between 23 and 35 days; that sperm only live or are mobile for five days; that the egg is impossible to fertilise more than 48 hours after ovulation; that the product can accurately detect rises in the hormones; and that these changes can predict ovulation sufficiently early to prevent sperm being deposited in the female reproductive tract.
They will also point out that there was only one study into Persona and that, while it initially assessed 710 women, it only came up with full results for 358 of those; that the women were selected so that only 15% of the youngest, and most fertile, women were included; and that, since there was no control trial, it was inadequate. Their lawyers will argue that Persona was wrong to market itself as being as safe as a condom, which is 98% reliable - a claim made until August 1997; and that it should have included later warnings that it was not suitable for women with polycystic ovarian syndrome, liver or kidney disease or on certain medication from the time it went on the market. "It was presented as the ideal, non-invasive way of controlling your fertility," says Williams. "But it has since emerged that there are some women for whom this could never have worked."
Unipath's director of external affairs, Dr Jayne Ellis, refuses to be drawn on the validity of the research or any aspect of the case, for legal reasons, though she stresses that Unipath had clearly indicated it had a 94% success rate from the start, that it was suitable for women in stable relationships, and that many women were "very happy with it and the benefits it offers".
It is left to Toni Belfield, of the FPA, formerly the Family Planning Association, to point out that, as with any contraceptive device, there is room for human error. "Persona represents more than 15-20 years of research, so it is not as if this has been brought about quickly, but it still has a 6% failure rate when used correctly. The problem is that women don't understand failure rates and think that when a product is a nice-looking piece of technology, it is infallible.
"But all the feedback we have received suggests women don't understand it. They say: 'I had sex on the first red day, but that is OK isn't it, because the machine will allow for it,' presuming there is some leeway. Or they say: 'I don't mind getting pregnant but I didn't want it to be in the first month,' not understanding that this was a possibility. They break the rules and you can't do that with contraception."
These arguments hold little sway with Mandy Mayes or Clare Browne, 35 (not her real name), an Oxbridge academic also involved in bringing the action, who argue that they were scrupulous in following the instructions and that their pregnancies were down to method error.
Browne, who became pregnant with her now four-year-old son three months into using Persona, is particularly emphatic in stressing that she did not make a mistake. "I'm au fait with technology - I have run an IT department - and I understood there was huge room for user error, so by the time I started using Persona I knew the leaflet back to front. I'm an academic. I do detail. And I had invested quite a lot of money in this technology, so why would I do it half-heartedly?"
Since becoming pregnant (when the machine continued to flash green despite her skipping a period), she has scrutinised the research papers, and concludes: "So many assumptions have been made that, if I were an expert in this field and I had been responsible for this, I would worry that I'd never work again."