Fetal dolphins are, apparently, easy to get on camera, but for elephants the procedure is rather more convoluted and involves shoulder-length rubber gloves.
The pictures of live animal fetuses were created for broadcast at Christmas on Channel 4 in Britain and the National Geographic Channel in the US.
They were recorded from the point of fertilisation through to birth, and the elephant can be seen growing from a single cell to a 118kg newborn.
One of the world's leading ultrasound experts, Thomas Hilderbrandt, was brought in by the producers to record four-dimensional images from inside the wombs of dogs, dolphins and elephants.
The dogs would lie down for the procedure and the dolphins were trained to swim against the ultrasound equipment, but the elephants had to be given an enema before a probe was pushed up the rectum to get close enough to the fetus to generate images.
Jeremy Dear, of Pioneer Productions, which made the 90-minute program, said the star sequence was a computer-generated scene of the elephant fetus moving down the birth canal, before switching to a live exterior shot of an elephant birth.
"It gets an 'ahhh' every time," he said. "It's anthropomorphism gone mad, but it's very effective.
"The key to this is that it opens up this unseen world of the animal womb.
"The reason we got such co- operation from zoos and vets in making the film is that they were really keen to see what actually goes on in the womb. What we've done is make it visual."
Several animals of each species were used to create the images, but the pictures were mixed together to provide viewers with a sequential story following the creatures from the moment of their conception to birth.
The golden retriever can be seen panting in the womb with its tongue hanging out, and the dolphin fetus can be seen at eight weeks, the point at which it starts to learn to swim. It has another 10 months before birth.
During the program, evolutionary stages from millions of years ago can be seen. Leg-like buds appear on the dolphin, then vanish. Similarly, the elephant develops ducts normally found in freshwater fish.
"The film underlines some fascinating facts about our evolutionary heritage and you can't help be moved by each of our animal's journeys towards birth," Mr Dear said.
"Via a combination of advanced technology, in-depth timeline of each fetus's development and birth, and state-of-the-art computer-generated graphics, Animals in the Womb offers a pretty extraordinary window on this previously unseen world."
Güncelleme Tarihi: 20 Eylül 2018, 18:16