One in five women with silicone breast implants will need them removed or replaced within five years, according to the latest data from the U.S. Food and Drug Administration.

But they're still relatively safe, said the FDA in its first report into the safety of implants since they were returned to the market in 2006.

"Based on the totality of the evidence, the FDA believes that silicone gel-filled breast implants have a reasonable assurance of safety and effectiveness when used as labelled," the FDA report said.

"Despite frequent local complications and adverse outcomes, the benefits and risks of breast implants are sufficiently well understood for women to make informed decisions about their use."

For the 14 years prior to 2006, only saline-filled implants were permitted under U.S. law, largely due to concerns that silicone implants were linked to cancer and lupus, among other diseases.

The new FDA data showed that among women who receive implants for cosmetic purposes, 20 to 40 per cent will need repair or removal work within a decade.

And among women who have breast implants for reconstruction purposes, after surgery for breast cancer, for example, the number climbs to between 40 and 70 per cent.

"Although routine replacement is not necessary, many women will need additional surgery to modify, remove, or replace their implants," said the FDA study.

Frequent complications include implant rupture, wrinkling, asymmetry, scarring, pain and infection, the report said.

Scar tissue can also harden around the implant, warping the shape of the breast.

The study said there is no apparent connection between silicone gel implants and connective tissue disease, breast cancer or reproductive problems.

However the study added: "Associations that are very rare or that take many years to manifest may not be detected using currently available data."

Dr. Wayne Carman, a plastic surgeon and former president of the Canadian Society for Aesthetic Plastic Surgery, put a positive spin on the numbers.

"What they've said is one out of five women will require replacement or removal of breast implants in the next 10 years, and they make it sound as though that's a pessimistic statement," Carman told CTV's Canada AM.

"Turning it around one might say four out of five women do not need to have their implants replaced after 10 years, and that 80 per cent of women are fine after 10 years."

In his own experience performing "several thousands" breast augmentations over the past 25 years, Carman said the number of women who require removal or replacement within 10 years is closer to 5 per cent across all classes.

When the FDA returned silicone gel implants to the market in 2006, it required manufacturers to complete studies on patients who received the implants.

Its latest approval is based on the results of those studies, though most are incomplete and have seen high dropout rates among participants.

One study of 1,000 women can only account for 58 per cent of those originally enrolled eight years ago.

Two other larger studies of 40,000 women, conducted by manufacturers of the silicon implants, have each experienced a high drop out rate after two to three years.

Dr. Diana Zuckerman of the National Research Center for Women and Families, told The Associated Press that most medical journals would not consider the studies valid due to the missing data.

"Once a medical product is approved, the manufacturers have no incentive to do these required studies properly," Zuckerman said. "So, we end up with useless information, which is what has happened with the largest, most important studies of silicone gel breast implants."

The FDA study suggested that women who are considering getting breast implants should recognize they are not "lifetime devices."

"The longer you have your implants, the more likely it will be for you to have them removed," the study said.