Final answer:
Head lag is typically resolved by the age of 6 months, and persistence beyond this age may indicate developmental issues. Stunting refers to being significantly below the median height for age and also suggests developmental concerns.
Step-by-step explanation:
Head lag in infants is a condition when the baby cannot lift their head up while being pulled from a lying to a sitting position. It is part of normal development during the first few months of life. By the age of 4 to 6 months, infants typically gain enough strength and control to hold their head up without it lagging behind. Head lag after 6 months of age can be a concerning abnormal finding and may indicate developmental delays or other health issues. Similarly, stunting is a growth deficit diagnosed in children who are at least two standard deviations below the median height for their age in a reference population. This can represent a significant deviation from expected developmental milestones and often requires further evaluation by a healthcare professional.