Persistent low heart rate in a baby since birth should be assessed by a pediatrician promptly, ideally today or within 24 to 48 hours if the baby otherwise appears well. A single low reading during deep sleep can be normal, but a repeatedly low rate while awake, or a rate that has been low since birth, needs an ECG to identify the rhythm.

Seek emergency care now if the baby has any of these:

In a newborn, persistent heart rate below 80/min is generally considered bradycardia and warrants evaluation. The heart rate normally changes substantially with activity and sleep in neonates and infants. A textbook notes that bradycardia with normal circulation and no evidence of heart block often does not need treatment, but the “since birth” pattern still needs the rhythm documented with an ECG. Tintinalli's Emergency Medicine: A Comprehensive Study, p. 883. The AAP newborn guidance likewise defines persistent newborn bradycardia as below 80/min.

Possible explanations range from benign sinus bradycardia, especially during sleep, to issues that need treatment, including:

A clinician will usually check oxygen saturation, blood glucose and temperature, examine perfusion and heart sounds, and perform a 12-lead ECG. Depending on results, they may arrange an echocardiogram, Holter monitor, and blood tests. If there is a family history of fainting, sudden unexplained death, long-QT syndrome, pacemaker use, or maternal lupus/anti-Ro or anti-La antibodies, mention it specifically because it changes the assessment.

If you reply with the baby’s age, actual heart-rate readings, whether they were asleep or awake, feeding/breathing symptoms, oxygen saturation if known, and whether an ECG has been done, I can help interpret how urgent it sounds.