New U.S. guidelines say freezing human eggs for fertility can work -- but they still urge caution for women hoping the technology will pause a ticking biological clock.

Egg freezing had been labeled experimental, but Friday's guidelines say that is no longer the case. The American Society for Reproductive Medicine cites studies showing younger women are about as likely to get pregnant if they used frozen eggs for their infertility treatment as if they used fresh ones.

The move is expected to help cancer patients preserve their fertility and to boost donated egg banking. But the group stopped short of endorsing egg freezing solely to defer childbearing, saying it is not clear who is a good candidate as older women do not fare as well.