Researchers studied 86 mother-infant pairs in a neonatal intensive care unit in Meir Hospital in Israel.
Compared with preterm infants whose mothers just held them with direct skin-to-skin contact but did not sing, infants whose mothers both held them and sang to them had improved heart rate variability patterns.
This combined effect of holding and singing also caused mothers to feel less anxiety.
"We recommend combining kangaroo care and maternal singing for stable preterm infants," said Dr Shmuel Arnon, lead author of the study published in the journal Acta Paediatrica.