An important aspect of the care of the newborn is a thorough, detailed physical examination that identifies normal characteristics and existing abnormalities and establishes a baseline for future physiologic changes. The physical assessment of the neonate should be one of the doctor's priorities in the plan of care. This article focuses on normal findings, variations from the norm that require little or not therapy, and specific potential danger signs that should alert the doctor to more careful observation of the infant. In some facilities estimation of gestational age is a routine procedure.
General measurements
There are several important measurements of the newborn that have significance when compared to each other as well as when recorded over time on a graph. For full-term infant, average head circumference is between 34 and 36cm. Head circumference may be somewhat less immediately after birth because of the molding process that occurs during a normal vaginal delivery. Usually by the second or third day the normal size and contour of the skull have replaced the molded one.
Chest circumference is 32 to 34cm. Head circumference is usually about 2 to 3cm greater than chest circumference. Due to molding of head during delivery, these measurements may initially appear equal. However, if the head is significantly smaller than the chest, microcephaly or premature closure of the sutures (craniostenosis) should be suspected, If the head is more than 4cm larger than the chest in circumference and this relationship remains constant or increases over several days, then hydrocephalus must be considered. Other causes of increased head circumference are caput succedeneum, cephalhematoma, and sub-dural hematoma. Premature birth and malnutrition can cause the head measurement to be significantly larger than the chest circumference, but this is because of decreased chest size, not increased head circumference.
Head circumference may also be compared with crown-to-rump length, or sitting height. Crown-to-rump measurements are from 31 to 35cm approximately equal to head circumference. The relationship between the head and crown-to-rump measurements is more reliable than that between the head and chest. Head-to-heel length is also measured int he newborn. Due to the usual flexed position of the infant, it is important to extend the leg completely when ensuring total length. The average length of the newborn is 52 to 54cm.
Body weight should be taken fairly soon after birth because weight loss occurs fairly rapidly. Normally the neonate loses about 10% of the birth weight by 3 to 4 days of age because of loss of excessive extracellular fluid, meconium, and limited food intake. The birth weight is regained by the tenth day of life. Most newborns weigh 2700 to 4000g, the average weight being about 3200-3400g. Newborns who weigh below 2500g are generally classified as low-birth-weight infants. Accurate birth weights and lengths are important because they provide a baseline for assessment of future growth.
Another category of measurements is vital signs. Axillary temperatures are taken because insertion of a thermometer into the rectum can cause perforation of the mucosa. However, taking a rectal temperature or using the soft tip of a catheter provided an opportunity to determine potency of the anus. Core body temperature varies according to the periods of reactivity but is usually 35.5 degrees Celcius to 37.5 degree Celcius. Skin temperature is slightly lower than core body temperature.
Pulse and respirations vary according to the periods of reactivity and to the infant's behaviors but are usually in the range of 120 to 140 beats/minute and 30 to 60 breaths/minute, respectively. Both are counted for a full 60 seconds to detect irregularities in rate or rhythm. Heart rate is taken apically with a stethoscope. Blood pressure is usually not taken in newborns. However, the average systolic blood pressure is 70mm/Hg at 2 days of age, 84mm/Hg at 2 weeks, and 93mm/Hg at 6 weeks.
