Which of the following is a critical factor in assessing growth in infants?

Weight-for-Age is a critical factor in assessing growth in infants because it allows healthcare professionals to evaluate an infant's growth pattern relative to their peers across a range of ages. This measure provides insight into the nutritional status and overall health of the infant. It takes into consideration the weight in relation to age, which is particularly important in identifying growth deficiencies or excesses.

This metric is crucial in the early stages of life when rapid physical changes occur, as it can indicate potential issues such as malnutrition or metabolic disorders. By comparing an infant's weight against standardized growth charts, practitioners can identify if the infant is growing adequately for their age group.

Other metrics, such as head circumference, height, and weight-for-length, while also significant, focus on different aspects of growth and development. For instance, head circumference is vital for assessing brain growth, height is more relevant for older children, and weight-for-length is typically useful for assessing body composition. However, weight-for-age provides immediate insight into an infant's growth process relative to their expected developmental milestones.