About Normal Blood Pressure for an Infant

Blood pressure is an important factor in adult health, especially when considering heart disease and cardiac health, but blood pressure is important to the health of children and infants as well. Blood pressure fluctuations affect an infant's circulatory system, and a decline in pressure has been associated with sudden infant death syndrome, or SIDS.

Identification

• The force of the blood flowing through the heart into the arteries of the body is met by resistance as the arteries fight to hold the blood back, and this power struggle creates blood pressure, which is identified by two numbers. The higher number is called the systolic, which represents the heart's contractions as it pumps blood during a heartbeat, and the lower number is the diastolic, representing the heart at rest.

Normal Blood Pressure

• Crying and sleeping can alter blood pressure, but there is an average range for all infants; the systolic and the diastolic number rise with age. A newborn has a normal blood pressure of about 70 over 42, but when the infant reaches 1 month of age, the normal blood pressure rises to approximately 85 over 45. At 6 months of age normal blood pressure is 93 over 55, rising again at 1 year to a normal average of 94 over 56.

Measurement

• Infant blood pressure can be measured in two ways. The in-dwelling method places a catheter inside the infant's body and is the most reliable way of measuring blood pressure; the oscillometric method is very non-invasive and measures blood pressure using a cuff that can be placed around the infant's arm or leg. The best time to take blood pressure measurements non-invasively is during sleep.

Theories/Speculation

• The sleeping positions of an infant may affect blood pressure. For instance, an infant who is put to sleep on his belly will sustain a decline in blood pressure, while an infant who is laid on his back sustains no blood pressure changes. The correlation between babies who sleep on their stomachs and SIDS may signify that the drop in blood pressure plays a role in this devastating syndrome. This blood pressure drop is most crucial between the ages of 2 and 3 months, when SIDS is most prevalent.

Expert Insight

• The blood pressure ranges of a full-term infant are significantly higher than those of a preterm infant. While the normal resting blood pressure for a full-term newborn is 70 over 42, the normal resting blood pressure for a premature baby can be as low as 63 over 35. The difference has led researchers to believe that the normal resting blood pressure of infants varies greatly depending on age, gestation and birth weight.