INTRAUTERINE DEVICES (IUDs)

An intrauterine device (IUD) is a little, t-shaped piece of plastic inserted into the uterus to prevent pregnancy. There are hormonal and non-hormonal options available, depending on an individual’s health concerns and preferences.

HORMONAL IUDS

TYPES

There are four different types of hormonal IUDs that deliver varying levels of progestin to the uterus to prevent pregnancy:

  • Mirena - prevents pregnancy for up to eight years

  • Liletta - prevents pregnancy for up to six years

  • Kyleena - prevents pregnancy for up to five years

  • Skyla - prevents pregnancy for up to three years

MECHANISM

A hormonal IUD releases a controlled amount of progestin, a synthetic form of the hormone progesterone, into the uterus over several years. The progestin thickens cervical mucus, making it difficult for sperm to reach the egg. It also thins the uterine lining, making the uterus less suitable for implantation. Importantly, the hormonal IUD primarily prevents fertilization and has a local effect within the uterus, with minimal systemic hormonal exposure. It is highly effective as a long-term contraceptive option.

NON-HORMONAL IUD

TYPE

The only non-hormonal IUD available is a copper IUD, also referred to as Paragard.

MECHANISM

Unlike hormonal IUDs, a copper IUD does not contain hormones. Instead, it has a small copper wire wound around its stem. The copper creates an environment that is toxic to sperm, impairing their mobility and viability. This prevents fertilization from occurring. Copper IUDs can also be used as emergency contraception if inserted within a few days after unprotected intercourse. When used in this way, copper IUDs may affect the ability for sperm to reach an egg and for a fertilized egg to implant in the uterus, providing an emergency contraception option that can be more effective than hormonal emergency pills if inserted promptly.