Fetal X-ray of a dolphin
Dolphin females ovulate only 2-4 times a year (affected by water temperatures, food and other environmental and social factors). Dolphins like humans, have sex not only with the aim of generating progeny but also as a way to generate strong ties.
The gestation of a dolphin lasts 1 full year (ie 12 months in the belly).
via Ardea Iniciativas y Estudios Ambientales