Spanish Eurovision contestant Soraya Arnelas sang 'All I Want For Christmas Is You' and 'White Christmas', while 10 pregnant women watched, before joining her on stage for a dance.
The mums-to-be were all using speaker-like devices called BabyPods, which are worn like a tampon and connected to a smartphone.
The phone acts like a microphone, to transmit the sound inside the vagina via the BabyPod.
Eurovision contestant Soraya Arnelas performed in the "vaginal concert"
Arnelas said that as someone who considers herself a "future mummy" this was a great opportunity.
"I've never been performing for such a young audience, so it's been a very special show," she said.
One mum in the audience, Soraya Korkar said: "It was the first time I experienced something like that, it was really amazing.
"It was unique."
The BabyPod is worn inside the vagina, like a tampon
It's set at a volume of just 54 decibels – which the makers say is equivalent to a hushed voice or soft, ambient music.
The material coming into contact with the mother’s body is silicone, which is hypoallergenic and the makers state that the first 100 children using Babypod have already been born and their hearing tests at birth have been normal.
Dr Helen Webberley, GP for Oxford Online Pharmacy, told HuffPost UK Parents that in theory the device will transmit more sound to the baby than through the abdomen, however, she cautions there may be risks.
"Between the womb and the abdominal wall are the bowels which are full of gas and therefore hinder the transmission of sound waves," she explained.
"Therefore the theory goes that if you can put the source of sound closer to the womb, i.e in the cervix, then the sound will transmit better.
"There are still questions however, about the evidence that playing sound actually has any measurably positive effects on the growing baby, and whether these effects are lasting or just eyelid flicker responses?
"From a medical perspective it also raises the question of infection and risk to the pregnancy, in terms of premature labour, and research would need to be done on this to fully evaluate the implications."