When curious cubs with boundless energy explore the frozen terrain of the Arctic, trouble is not far behind.
Mother polar bears are pregnant for about eight months at a time and they usually give birth about every three years. In order to become successfully pregnant, mother polar bears must gain at least 441 lbs or 200kg, to support her cubs.
Mother polar bears almost always give birth to twins, but they have a one percent chance of giving birth to triplets. The scientific process of the baby development in the mother includes a period of delayed implantation.
The fertilized egg divides into a hollow ball of cells one layer thick (a blastocyst),and then stops growing and it lies free-floating in the uterus for about four months. After this period of time, the blastocyst then implants in the uterine wall and continues to develop.
The embryonic development (the making of the cub in the uterus) takes about four months. The reason for delaying implantation is so that the cub will be born during the best time of the year for survival and it allows the female to get into good physical condition and use her energy for nursing her newborn cubs.(Source)