Hundreds of Australian women have fallen pregnant while using a popular contraceptive implant that is meant to be effective for three years.
A spokeswoman for the Therapeutic Goods Administration said it had been notified of 768 suspected problems involving Implanon, including 498 pregnancies since it became available in 1999.
The outcome of most of the pregnancies is unknown, but the spokeswoman said 29 women had suffered miscarriages and 17 had ectopic pregnancies (a fertilised egg that develops outside the uterus).
The 498 pregnancies represent fewer than one in a thousand of the 633,000 devices that have been dispensed through the Pharmaceutical Benefits Scheme since 2001.
The TGA and fertility experts said yesterday the figures should not alarm people using or considering using the device because they showed it was extremely reliable compared with other contraceptives such as the pill or condoms, which are about 92 per cent effective.
A professor of obstetrics and gynaecology at the Royal Women's Hospital and Melbourne University, Martha Hickey, said Implanon had been a very safe method of contraception and that most failures were likely to be caused by errors in its application. There was also no evidence the device would harm a foetus if a user became pregnant, she said.
Professor Hickey said a 2005 study showed that about a quarter of 200 women who fell pregnant when using the device had been pregnant before it was implanted. The study also found that 127 of the women had not had the device properly inserted.
A senior medical officer at Family Planning Victoria, Dr Kathy McNamee, said she believed some Australian women had brought legal action, but she did not know the details and suspected the cases were settled out of court.
A spokesman for Implanon's manufacturer, MSD, would not comment on the legal action, but said the company was confident its product was safe and effective. He said a review of nine years of data showed there had been 0.049 pregnancies per 100 implants sold.
''Implanon is more than 99 per cent effective,'' he said.