Women need to beware that while breast implants are safe, they are not meant to last a lifetime and could lead to problems later on, the top US drug agency said.

"Breast implants are not lifetime devices. The longer a woman has silicone gel-filled breast implants, the more likely she is to experience complications," the US Food and Drug Administration said in a report.

The FDA approved the sale of silicone breast implants in November 2006 for women age 22 and above.

But in updated safety guidelines it warned that one in five women who have had breast implants to increase their cup-size or for reconstruction surgery will have to undergo another operation within 10 years.

"For patients who received implants for breast reconstruction, as many as one in two will require removal 10 years after implantation," the report said.

And one in five patients who received implants to boost their appearance will need them removed within 10 years.

Most complications occur from hardening of the breast tissue around the implant, from a rupturing of the implant, or "wrinkling, asymmetry, scarring, pain and infection," the FDA said.

It stressed its preliminary investigation showed no risk of cancer or any reproductive problems linked to breast implants, but recommended that there should be further studies.

The American Society of Plastic Surgeons said that last year 390,000 breast implant operations were carried out, the vast majority to increase bust size. Those figures include both silicone implants and those filled with saline water.

"The FDA will continue to monitor and collect safety and performance information on silicone gel-filled breast implants, but it is important that women with breast implants see their health care providers if they experience any symptoms," said Jeffrey Shuren, director of FDA's Center for Devices and Radiological Health.

"Women who have enrolled in studies should continue to participate so that we may better understand the long-term performance of these implants and identify any potential problems."