Expectant parents can watch a video of their unborn baby scratching its nose, sucking its thumb and even hiccupping in the womb.
The Voluson®730 scanner shows in minute details the activities and even the facial expressions of the baby within the womb.
The scan, which is not available on the NHS and costs £220 a time, is mainly for the pleasure of parents, but it can also be invaluable in picking up abnormalities such as cleft palate.
Professor Stuart Campbell, head of obstetrics and gynaecology at St George's Hospital Medical School, has pioneered the 4-D ultrasound scanning. It is so-called because the baby can be seen moving in three dimensions.
He said: "The scan provides completely different information from the 2-D black and white ultrasound images that all women are offered at 12 and 20 weeks of pregnancy.
"The 2-D scan is excellent at showing the structure of the internal organs but the 4-D gives better views of the surface features such as the face, limbs, hands and feet and also the baby's skull, spine and skeleton.
"It enables all the fingers and toes to be counted.
"As a result 4-D scanning provides more information on certain abnormalities such as cleft lip and palate.
"One woman I scanned, whose baby had a cleft palate, wanted to take pictures to a surgeon to discuss the surgery after birth.
"Parents often don't know what such abnormalities look like so they have terrible mental images.
"The parents faced up to the reality of what a cleft palate looked like and bonded with the baby. It helped them come to terms with the problem long before the birth of the baby.
Professor Campbell said the technique was invaluable in enhancing the normal bonding process, allowing new parents to see a realistic picture of their child and to make an early bond.
It can also persuade parents to take more care of their children in their womb.
One mother said seeing her daughter in the womb had encouraged her to give up smoking.
"Until I saw the video of Katy at 20 weeks old, I could not relate to this lump growing inside me enough to want to give up my cigarettes.
"But as soon as I saw the beautiful pictures of my daughter, it felt criminal to do anything which might cause her harm.
"I stopped smoking straight away, gave up my glasses of wine and concentrated on making myself as healthy as possible to give Katy the best possible start in life."