Answer:
After mating, female bottlenose dolphins start the gestation period which lasts approximately twelve months.
After this time, a single calf is born, usually with the help of another female dolphin which assumes the role of a midwife.
Dolphin mothers give birth to the calf by releasing the tail of the offspring first, to avoid that the new dolphin gets drown.
The mother nourishes the calf for up to 18 months with milk produced by her body.
After weaning, young dolphins stay with their mothers for around six years until they have developed all the skills for hunting and surviving.