Final answer:
Growth faltering due to undernutrition typically occurs between conception and two years of age, leading to potential stunting, wasting, and other health issues.
Step-by-step explanation:
Most growth faltering due to undernutrition, which can lead to stunting, occurs between the ages of conception and two years of age. This period is crucial as it encompasses prenatal development and early infancy, where essential nutrition is required for proper growth and development. Children suffering from undernutrition during this sensitive phase may experience wasting (loss of muscle and fat) or stunting, which is when a child is too short for their age due to chronic undernutrition. If a growth deficit begins in utero due to maternal undernutrition, it can result in a low birthweight, making the child more susceptible to disease, stunting, and developmental delays throughout early childhood.