Hundreds of women have become pregnant after a long-term contraceptive implant failed to be properly inserted, the government’s drugs and medical devices watchdog said on Wednesday.

Since Implanon, a hormone-filled tube inserted in the arm, was first authorized in 1999, a total of 584 women have reported unwanted pregnancies, the Medicines and Healthcare products Regulatory Agency (MHRA), said.

In all, 1,607 women have complained about the device, largely concerning adverse reactions such as scarring and other problems.

NHS Trusts have paid nine women a total of nearly 120,000 pounds in damages, with a further 80,000 pounds in costs, the Department of Health said.

Implanon, which is the size of a matchstick and inserted in the inside upper arm, contains synthetic progestogen and should offer three years of protection, if administered properly.

But the plastic tube, which can be inserted by doctors and nurses, were implanted too deeply or became dislodged in some cases.

Implanon has since been replaced by Nexplanon, which has a pre-loaded applicator for easier insertion. It has not been removed from the market and will continue to be administered until stocks run out, the MHRA said.

Implanon, manufactured by MSD, a subsidiary of pharmaceutical giant Merck, was reported to be particularly popular among young women, who are more liable to forget to take daily contraceptives.

If administered correctly, Implanon is more than 99 percent effective, the same rate as the pill.

About 1.4 million women have used Implanon during the past 12 years.

The Department of Health moved to reassure couples, saying “the vast majority of people with the implants experience safe and effective care.”

“If something goes wrong, hospitals have a duty to report it and it is right that patients are compensated where appropriate,” it added in a statement.

Stephanie Prior, a lawyer at Anthony Gold, who represents three women, said it was possible others could come forward, and questioned the continued use of Implanon without further training.

One of her clients was forced to terminate her pregnancy while another had a miscarriage, which led to both suffering a breakdown in their relationships, she said.

The manufacturer said in a statement: “MSD is confident in the efficacy and safety of Implanon.

“Since its initial approval in September 1999, over 1.3 million units have been prescribed in the UK. Although no contraceptive is 100 percent effective, Implanon is more than 99 percent effective.

It said a review of nine years of data had indicated five pregnancies per 10,000 implants sold.

“The basis for successful use of Implanon is a correct and carefully performed subdermal insertion of the implant in accordance with the product instructions.”

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Avril Ormsby