Normal Heart Rate for a 1-Month-Old Infant

The normal heart rate range for a 1-month-old infant is 107-182 beats per minute (bpm), with a mean of 149 bpm. 1

Age-Specific Heart Rate Parameters

For infants 7-30 days of age, the European Society of Cardiology guidelines establish a normal heart rate range between 107-182 beats per minute, with a mean of 149 bpm 1
The 2nd percentile (lower normal limit) is 107 bpm, while the 98th percentile (upper normal limit) is 182 bpm for infants in this age group 1, 2
By comparison, in the first week of life, the normal range is slightly lower at 91-166 bpm 1, 2
As infants grow to 1-3 months of age, the range shifts to 121-179 bpm, with a mean of 150 bpm 1

Heart rate varies significantly based on the infant's state:
- Awake vs. sleeping: Heart rate is approximately 5.6 bpm higher when the infant is awake compared to when sleeping 3
- Position: Heart rate is about 4.9 bpm higher when the infant is on the mother's chest compared to being in a cot 3
- Gender: Girls typically have heart rates approximately 1.6 bpm higher than boys 3
- Temperature: Heart rate increases by about 0.5 bpm for every 0.1°C increase in rectal temperature 3

Sinus tachycardia (heart rate above 182 bpm in a 1-month-old) may indicate conditions such as:
- Fever, infection, anemia, pain, dehydration, hyperthyroidism, or myocarditis 1
- Newborn infants may transiently reach heart rates up to 230 bpm during periods of distress 1
Sinus bradycardia (heart rate below 107 bpm in a 1-month-old) may indicate:
- Central nervous system abnormalities, hypothermia, hypopituitarism, increased intracranial pressure, meningitis, maternal drug transfer, obstructive jaundice, or hypothyroidism 1
- A heart rate below 60 bpm with signs of poor perfusion requires immediate intervention 2

Individual heart rate can vary considerably during the first 24 hours of life (coefficient of variation 9.2%) 3
The maximum variation in heart rate for any individual during a 24-hour period ranges from 73 to 134 bpm (mean 100 ± 17) 4
Electrocardiography provides the most reliable measurement of heart rate when accurate assessment is needed 2
When evaluating neonatal heart rate, the clinical context and overall condition of the infant are more important than isolated measurements 2

Avoid misinterpreting transient bradycardia during feeding, sleep, or defecation (due to increased vagal tone) as pathological 1
Be cautious not to mistake blocked atrial bigeminy for true sinus bradycardia 2
Remember that normal ranges are statistical constructs - the use of 2nd and 98th percentiles to define normality implies that 4% of normal infants will have values outside these ranges 1
Measurement artifacts are common in neonatal monitoring and can lead to inaccurate readings, particularly with movement, hiccoughs, or electrical interference 1