Skyla and Mirena are pretty similar, but Skyla lasts for up to 3 years while Mirena lasts for up to 8 years. Also, Skyla is slightly smaller than Mirena and [was FDA-approved for women who've never had a child](https://www.bedsider.org/features/261), though both IUDs are totally safe for most women to use, regardless of their parental status.