WASHINGTON (Reuters) — The contraceptive Norplant, which has been off the U.S. market since September after tests showed a batch of the implants may not work, proved to be a safe and effective method of birth control in a study carried out in eight developing countries, researchers said Saturday.

A study by the U.N. World Health Organization and the Population Council, a nonprofit group devoted to population issues, of nearly 8,000 Norplant users found no serious side effects to users of the contraceptive and said its effectiveness against pregnancy was better than 99 percent per year.

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Researchers said they did find slightly higher rates of high blood pressure and gall bladder disease in Norplant users than in a control group of women who used IUDs or were sterilized.

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