Depends: The Mirena (levonorgestrel) releases progestins directly into the uterus. That thins the lining of the uterus so that a fertilized egg cannot implant. It also causes thicker cervical mucous that obstructs sperm travel, and decreases tubal motility inhibiting the sperm and egg from meeting. The copper t causes inflammation in the uterus that kills the sperm so that conception can't occur.
Answered 10/4/2016
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