The American Mink reproduces in the spring time, they also have he ability to delay the implantation after mating to ensure that they give birth in the spring.
The American Mink is also not monogomus, the females take care of their young and the males continue on in their lives elsewhere.
The American Mink on average carries their young before giving birth from 40-75 days. Their average amount of you g to give birth to is 8.