IUD With Progestogen - Mechanisms of Action

Mechanisms of Action

The hormonal IUD's primary mechanism of action is to prevent fertilization. The levonorgestrel intrauterine system has several contraceptive effects:

• Cervical mucus thickens
• Sperm's survival and ability to penetrate the egg is inhibited
• Endometrium is suppressed
• In some women, ovulation is inhibited

Numerous studies have demonstrated that IUDs primarily prevent fertilization, not implantation. In one experiment involving tubal flushing, fertilized eggs were found in half of women not using contraception, but no fertilized eggs were found in women using IUDs. IUDs also decrease the risk of ectopic pregnancy, which further implies that IUDs prevent fertilization.