Astonishing images from inside the womb produced by new technology show babies apparently smiling and crying.

New technology reveals behavior of unborn (Courtesy Sky News)

The breakthrough in ultra-sound techniques, known as 3D and 4D scanning, could lead to advances in baby health for a whole range of conditions, including Down's Syndrome, reports Sky News.

Captured images offering new insight into fetal behavior show babies yawning, blinking, sucking their fingers and seeming to cry and smile, the British news channel said.

Traditionally, doctors have assumed infants made facial expressions, such as smiling, only after birth by copying their mother.

"There are many questions that can now be investigated," said Prof Stuart Campbell, a London obstetrician who pioneered the new techniques at the Create Health Centre for Reproduction and Advanced Technology.

"Does the fetus smile because it is happy, or cry because it has been disturbed by some event in the womb?" Campbell asks, according to Sky News.

His pictures reveal fetuses moving their limbs at just eight weeks.

Campbell says the new images could help answer questions such as, "Do babies with genetic problems such as Downs Syndrome have the same pattern of activity as normal babies?

Also, he wonders, "Why does a fetus blink when we assume it's dark inside the uterus?"