Hospital managers have insisted that a dog allowed on to a maternity ward while its owner gave birth was there as a therapy dog and not as a pet.
They said the pregnant woman was allowed to bring her labrador - called Barney - into the delivery room at St Michael's Hospital in Bristol because of his "calming presence".
But a source told the Sun newspaper that there were concerns from some of the medics that delivery room hygiene was put at risk.
The hospital said Barney regularly visits wards in his role as a therapy dog and approval had been sought from its infection control experts.
Sarah Windfeld, head of midwifery at the hospital, said: "Barney is a certified Pets as Therapy (PAT) dog and with his owner regularly attends to patients in hospital. PAT dogs are examined and passed on health, temperament, suitability and stability grounds and patients can benefit from their calming presence.
"His owner made the request to us at St Michael's Hospital for Barney to be present when she gave birth, as a therapy dog not as a pet. Having first sought the approval of our infection control experts, we agreed to Barney sitting nearby in the delivery room."
Ms Windfield added that thorough cleaning was done after the birth, as is usual practice at the hospital.
It is understood that Barney stayed for the birth, along with the woman's partner and a midwife, before the family took their newborn child home.
A source told the Sun: "Nurses and doctors were appalled but someone at the hospital had given the woman permission so the dog stayed with her in the labour ward. This is the first time any of the hospital's maternity staff can remember such a thing happening. Apparently she wanted the dog with her so there could be a family bonding experience."
The source added that while hygiene was their main concern, they were also worried this could set a precedent, prompting other requests.