The measurement of an infant’s head circumference, formally known as occipitofrontal circumference (OFC), is a standard procedure performed during routine well-child visits. This measurement tracks the distance around the largest part of a baby’s head, including the forehead and the most prominent part of the back of the skull. Healthcare providers use a flexible, non-stretchable tape measure to obtain this figure, which is then recorded in the baby’s health record. The OFC is a primary indicator of physical growth, alongside the infant’s weight and length, establishing a baseline for monitoring the child’s development over the first few years of life.
The Purpose of Monitoring Head Growth
Head circumference measurement is a screening tool for neurological development because the size of the skull directly reflects the growth of the brain underneath. The infant skull is composed of several bony plates joined by flexible sutures, allowing the head to expand rapidly in response to brain growth. Tracking this expansion provides insight into whether the brain is growing at an expected rate.
Brain development is most rapid during the first three years of life, making consistent tracking particularly important during this period. Abnormal growth patterns can signal potential underlying health issues. For instance, a head size significantly smaller than average, called microcephaly, may suggest the brain is not developing properly.
Conversely, a head growing much faster than expected, known as macrocephaly, could indicate fluid accumulation, such as in hydrocephalus. Routine measurements allow for the early identification of these growth deviations. Early identification allows physicians to order further diagnostic testing and intervene promptly if a neurological problem is confirmed.
Step-by-Step Measurement Technique
Accurate measurement requires a flexible, non-stretchable measuring tape and a calm infant. The goal is to find the maximum circumference of the head. The infant should be positioned comfortably, either held securely by a caregiver or lying flat.
The measuring tape must be placed just above the eyebrows, over the glabella (the area between the eyebrows). The tape is then wrapped around the sides of the head, ensuring it remains above the ears. It is brought to the back of the head, crossing the most prominent part of the occiput, which is the bony protrusion at the back of the skull.
The tape must be snug against the skin without compressing the scalp, and kept level and parallel to the floor around the entire circumference. The measurement is read where the tape overlaps itself, recorded to the nearest tenth of a centimeter (0.1 cm). To ensure reliability, the measurement is repeated three times, and the largest reading is the one recorded.
Interpreting Infant Growth Charts
The single numerical measurement is significant only when plotted on a standardized growth chart. These charts, often based on data from the World Health Organization (WHO) or the Centers for Disease Control and Prevention (CDC), display curved lines representing percentiles for head circumference by age and sex. A percentile indicates the percentage of infants of the same age and sex whose head circumference is less than the measured value.
For example, the 50th percentile means the infant’s head circumference is average for the reference population. More important than a single measurement is the rate of change or the growth curve over time. A child whose circumference consistently tracks along a specific percentile line (e.g., the 25th or 75th) is considered to be growing normally.
Concern arises when an infant’s growth line rapidly crosses percentiles, accelerating sharply upward or decelerating steeply downward across two or more major lines. This change in growth velocity is a red flag, prompting a healthcare provider to investigate for potential issues like hydrocephalus or microcephaly. If parents notice an abrupt change in the growth pattern between scheduled checkups, they should consult with their pediatrician immediately.