Final answer:
The infant's weight and length gain is an example of normal growth; it falls within the expected developmental milestones for an infant's age, assuming proper timing between clinic visits.
Step-by-step explanation:
The infant's gain of 1.3 pounds and an increase in length by 1 inch since the last clinic visit is an example of normal growth. Infants typically gain about 28 g (1 oz) per day in the first two months, slowing down to about 0.45 kg (1 lb) per month thereafter. On average, a healthy baby doubles its birth weight by six months and triples it by twelve months.
Rapid growth in length is also expected, with infants growing approximately 2.5 cm (1 inch) per month in the first six months, followed by about 1.2 cm (0.5 inch) per month in the second six months. Hence, the described weight and length gain is within the typical range for an infant, indicating adequate nutrition and absence of health issues that might cause growth failure.
Conditions such as failure to thrive, malnutrition, and hyperthyroidism would generally be associated with either insufficient growth or excessive growth, not the standard progression seen in the scenario described.
For example, failure to thrive and malnutrition typically result in below-average weight and length gains, while hyperthyroidism could cause excessive weight loss or other health problems. The infant in question is exhibiting growth consistent with the expected developmental milestones for their age, assuming the time frame between the clinic visits is appropriate for such growth.