The mum and dad were caught with their pants and everything else down by a cleaner who heard moaning coming from a private room.
The worker told bosses at St Michael's Hospital, in Bristol, but was told there are no rules against having sex in a hospital bed.
The official policy is for couples to put a 'Do Not Disturb' sign on the door.
A hospital source told The Sun: "Other patients on the unit heard the commotion and were upset. The cleaner was utterly shocked.
"She was amazed to be told it was OK. The hospital's advice appears to be just to put a sign up - amazing."
Like herbal remedies and eating spicy food, sex is said to help induce labour in some cases.
But NHS advice says: "You may have heard that certain things can trigger labour, such as herbal supplements and having sex, but there is no evidence that these work.
"Having sex won't cause harm, but you should avoid having sex if your waters have broken as there is an increased risk of infection."
A hospital spokeswoman said: "Staff work hard to ensure privacy and dignity is maintained for all patients.
"Thankfully, we have not received any complaints or concerns in regard to this matter."
Last year, St Michael's Hospital was criticised for allowing a mother to bring a dog into the maternity ward so it could watch her give birth.
Managers justified the extraordinary action by saying that Barney, believed to be a Labrador, was a certified 'therapy dog' who had witnessed many births and had a 'calming presence'.