Hormone-releasing intrauterine devices (IUDs) prevent pregnancy through hormone secretion, unlike other IUD types that might use copper. Of the provided choices:
- Lippes loop: This is a non-hormonal, older plastic IUD.
- Multiload 375: This is a copper IUD that uses copper's sperm-killing properties, not hormones, for contraception.
- Cu 7: This is a T-shaped, copper-containing IUD that does not release hormones.
- LNG-20: This is the correct choice. LNG-20 is a hormone-releasing IUD that dispenses levonorgestrel (a progestin) to prevent pregnancy by thickening cervical mucus and hindering sperm movement.
Consequently, LNG-20 is the accurate selection from the given options.