Doubts have been expressed about the efficacy of a new contraceptive device recommended by the promoters of natural family planning methods. The Persona kit claims to identify the woman's fertile period, when intercourse should be avoided by women who do not want to become pregnant.
The manufacturers claim a reliability rate of 94 per cent, which could result in one in 17 users becoming pregnant. This compares with one in 50 using the contraceptive pill.
The British Medical Devices Agency (MDA), an agency of the British Department of Health, received a number of complaints about its effectiveness from users, GPs and Trading Standards Officers.
It also emerged last year that eight women who became pregnant after using Persona have been granted legal aid to sue Unipath, the manufacturers.
As a result the MDA carried out an investigation. But manufacturers, Unipath, did not make the results of its initial clinical trials available to the MDA. These trials formed the basis of its adjustment of the device before it went on the market. There were no further clinical trials after the adjustment of the software in the device.
"The 94 per cent reliability claim was therefore based on a retrospective analysis of data using software containing a mathematical model derived from the same data," noted the agency. "The MDA is not in a position to either substantiate or refute the claim of 94 per cent reliability."
Dr Sheila Jones, medical director of the Irish Family Planning Association, said the IFPA welcomed the product when it was introduced last year as a help to women practising natural family planning. But she agreed that it was not suitable for people for whom a pregnancy would be unacceptable.
"The failure rate of 6 per cent was on couples really committed to this kind of family planning," she said. "It is likely that those less committed would have a higher failure rate. It would be mainly used by couples using natural family planning for whom another baby would not be the end of the world. We haven't seen young women throwing away their pills."
The Persona kit, which costs £49.95, consists of a calculatortype device, complete with batteries, a number of sticks for testing urine and a 60-page explanatory booklet.
It works on the basis of information about the woman's cycle fed into the calculator. After a number of months it builds up a picture of her cycle and calculates her likely fertile days.
On these days a red light shows on the calculator. On days when she is not thought to be fertile a green light shows. On doubtful days the light is orange. On these days the urine sticks, which measure hormone levels, are used and the information on them converts the orange light to red or green.
"The more information you feed into it the more accurate it is," said Dr Jones. "This is what makes the device quite expensive, at £50 plus £10 a month for the urine sticks. You have to use up that batch every month." The pill costs £3 to £4 a month. "Contraception is all about choices, and it does give couples another choice," said Dr Jones.
A spokeswoman for the manufacturers acknowledged that eight British women had been granted legal aid for the first steps towards suing them, but said the company had not been told on what basis the action was being taken.
She pointed out that the MDA was not saying anything different from the manufacturers about the effectiveness of the product, and that the 94 per cent reliability rate was the same as one in 17 being at risk of becoming pregnant.
She urged users not to stop using it as the manufacturers' guidelines on its use remained valid.