The frequency of cardiac murmurs in early infancy has been studied in a large series of unselected infants. In the immediate postnatal examination, a murmur was heard in 1.7 per cent. With repeated examinations, however, at 6 and at 12 months of age, the proportion of infants in whom a cardiac murmur was heard at some time rose to 7.0 per cent of 5,017 full-term singlebirth infants and to 9.9 per cent of 364 premature single-birth infants. Non-white infants had a significantly higher prevalence of murmurs than did white infants at both the 6 and 12 month examinations.
Of the 71 full-term infants who had murmurs at the birth examination and were re-examined at both 6 and 12 months, 49 (69 per cent) had no murmurs at either of the later examinations.
Of the 150 full-term infants who had murmurs heard for the first time at 6 months and were re-examined at 12 months, 90 (60 per cent) had no murmur at the 12-month examination.
Of the total number of 353 murmurs heard in full-term infants, 166 were ultimately interpreted to be functional, and 25 to be organic murmurs. The remaining 162 were inconstantly present, and were probably all functional murmurs.
In our experience, a murmur heard at birth carries a 1:12 probability of congenital heart disease; if it is again heard at 6 months, this chance is 1:3; and if the murmur persists to 12 months, the chance is 3:5 that congenital heart disease is present. When a murmur is first heard at 6 months, and persists until 12 months, the probability of congenital heart disease is 1:7; and when a murmur is first heard at 12 months, the probability falls to 1:50.
Premature infants were found to be similar to full-term infants in all respects, insofar as their small numbers made comparisons possible.
Finally, the relative rarity of cardiac murmurs in the newborn period has been demonstrated once more.
Impact on parents of bronchiolitis hospitalization of full-term, preterm and congenital heart disease infants
