Almost all parents sing to their babies, but now new research is showing that premature infants in particular show real benefits from listening to lullabies and other forms of music.

Researchers at the Beth Israel Medical Center in New York have completed a study in which they found music, singing and simulated womb sounds all help to calm a premature baby's heart rate and help with its breathing and feeding.

Premature infants are often left alone in quiet, closed incubators, with the thinking being that it is best not to over-stimulate them.

But study author Dr. Aimee Telsey, a neonatologist at Beth Israel, says her study found that preemies who listened to music actually have improved heart rates, sucking behaviour, sleep patterns and calorie intake.

She says the idea isn’t to stimulate the baby but to soothe them.

“We’re still really interested in keeping the baby quiet and calm, just in a slightly different way,” she told CTV’s Canada AM from New York.

Telsey says one of the particularly important findings was that parental stress levels also dropped in response to the therapy, and the music helped parents and babies to bond.

The study involved 272 premature infants in neonatal intensive care units at 11 U.S. hospitals. All the infants had health issues such as breathing problems, bloodstream infections or were underweight.

The researchers had the preemies listen to live music that had been matched to babies' breathing and heart rates.

Joanne Loewy, the head of the hospital's Louis Armstrong Center for Music and Medicine, says the team was very deliberate in its choice of music.

“We wanted to break apart the elements of music. Music has timbre, rhythm, flow, phrasing. So we used three interventions,” she said.

The first was a lullaby. The researchers asked the parents to sing their favourite lullabies – what the researchers called their “song of kin.” If the song had a fast rhythm, the researchers showed the parents how to slow it down and turn it into a lullaby. If the parents didn’t have a favourite, they used “Twinkle, Twinkle Little Star.”

The researchers also brought in certified music therapists to use devices called Remo ocean discs and gato boxes, which replicated "whoosh" and heartbeat womb sounds. They then were synchronized the tempo with infants' breathing and heart patterns.

The babies listened to the music three times each week for two weeks. The researchers found that all three music approaches slowed the babies’ heart rates, though singing lullabies seemed to be most effective. Singing also increased the time babies stayed quietly alert.

Babies hearing lullabies their parents chose had better feeding behavior and gained more calories than those who heard “Twinkle, Twinkle, Little Star,” but the "Twinkle" babies had slightly more oxygen saturation in their blood.

Sucking behavior improved most when a two-tone heartbeat rhythm was played on the gato box, while the breathing rate slowed the most and sleeping was the best with the ocean disc.

The study results appear in the journal Pediatrics.

Loewy said that lullabies have long been known to soothe babies -- preemies or otherwise -- and calls them as “precious as mother’s milk.”

Telsey adds that the study found it was important for the gato box rhythm to be played live, rather than on a recorded CD.

“With live music, there was a give and take. You were able to see how the baby was responding and vary the sound and the tempo to the response of the baby,” she said. “And then the parents were really able to learn that and learn a lot more about infant.”