Elephant mothers had to be trained to sit next to the scanners, and cameras were inserted into the womb to take clearer pictures. At 16 weeks, the foetus begins to look like an elephant as it develops a trunk. Two weeks later it is seen exercising its trunk and legs, and ears that already detect sound start to grow.

By 12 months, the foetus is a replica of what will emerge 10 months later £ except it is just 45 centimetres long. Animals in the Womb, which also focuses on the early life of a dolphin and a dog, was made by the same team that produced Life Before Birth, about the growth of a human foetus. The filmmakers used digital technology to help produce the images.

Producer Jeremy Dear, of Pioneer Productions, said: "These kinds of images have never been seen before ... The film underlines some fascinating facts about our evolutionary heritage and you can't help but be moved by each of our animal's journey towards birth," Dear said. "It offers a pretty extraordinary window on this previously unseen world.

"One incredible thing about the early images is how the animal embryos are very similar to human ones. It shows we humans share a common mammalian ancestry early on in life," he said. Watching the animals in the womb gives a fascinating peek at evolutionary history. The dolphin's development gives a nod to its land-dwelling ancestors as tiny leg-like buds come and go in the first month.The bone structure of its fins bears a startling resemblance to human hands. Conversely, the elephant could have once lived in the sea. Scans on the four-month-old elephant embryo reveal kidney ducts that are more commonly found in freshwater fish and frogs.

"We worked with dozens of zoos and animal sanctuaries across the world. There were a lot of different challenges. But it has been worth it," Dear said. Of the sequence following the development of the elephant, he said: "When it is finally born there is not a dry eye in the house."

Telegraph