How should an infant's length be measured accurately?

Measuring an infant's length accurately is best accomplished when the infant is in a supine position (lying flat on their back) and aligned with a flat surface. This method ensures that the entire body is straight along the measuring device, typically a measuring board or a flat surface with clear measurement markings.

In the supine position, the infant's head is placed against one end of the measuring surface, and the body is extended straight out to allow for an accurate reading at the feet. This method minimizes movement and allows for precise alignment, which is essential because even small deviations can impact the measurement significantly.

Using a well-marked flat surface enables the caregiver to measure from the tip of the head to the heel accurately, ensuring consistent measurements across different visits and reducing the likelihood of errors that can occur if the infant is not held or aligned correctly.