Programme makers also reveal the moment at eight weeks when a baby dolphin learns to swim while in the womb. During the next few weeks, it develops flippers, a tail and a blowhole before being born after a year, and must be able to quickly swim to the surface to take its first breath of air.
Experts also found that at 24 days, the dolphin embryo develops tiny leg-like buds, which then disappear over the next two weeks.
After 11 weeks, the dolphin embryo's fins display bone structures resembling human hands, which experts believe may show that dolphin ancestors were land dwellers.
The footage also shows how many animal embryos are like human ones.
"The incredible thing about the early images is how we all look very similar - it is obvious we humans share a common mammalian ancestry very early in life," said Mr Dear.