Possible mechanisms of action of intrauterine devices

Chronic inflammatory changes of the endometrium which alter sperm transport and inhibit fertilization

Spermicidal and ovicidal effects of copper ions (copper IUD)

Thickening of cervical mucus which prevents sperm from traveling into the upper genital tract (LNG IUD)

Thinning and glandular atrophy of the endometrium, which inhibit sperm transport and fertilization (LNG IUD)

IUD: intrauterine device; LNG: levonorgestrel.

Data from: Stanford JB, Mikolajczyk RT. Am J Obstet Gynecol 2002; 187:1699.

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