What are the chances of getting pregnant a month after my mirena (levonorgestrel) expired?

Very little chance: The Mirena (levonorgestrel) IUD works all the way to the 5 year point. It should work the same when a woman is 1 month before the expiration date, or 1 month after that date. It doesn't suddenly stop working, but the amount of hormone released decreases after the 5 year point. There is a very small chance of pregnancy if a woman has Mirena (levonorgestrel)... Some sources say a 1% chance during the 5 year period of time.