How long is a polar bear’s typical pregnancy, including delayed implantation?

A polar bear’s typical pregnancy lasts about eight months, including a period of delayed implantation.

After mating, the fertilized egg does not immediately attach to the uterus. This delay allows the female’s body to time implantation and birth so cubs arrive during the Arctic winter, usually in a maternity den.

The actual embryonic development lasts only around four months after implantation. A female normally gives birth to one or two very small, helpless cubs, which remain in the den while they grow and nurse on their mother’s rich milk.

Pregnancy length is therefore often misunderstood. Counting from mating gives roughly eight months, but counting only active fetal development gives a much shorter period. Females usually emerge from the den with their cubs in spring.