A nurse is collecting data from a 6-month-old infant during a well-child visit. The infant weighed 3.26 kg (7 lb 2 oz) at birth. Which of the following is the anticipated weight at 6 months of age?

The correct answer is choice C. 6.8 to 7.7 kg (15 to 17 lb). Choice A rationale: This weight range is above the average for a 6-month-old infant. According to growth charts, the 50th percentile weight for a 6-month-old male is approximately 7.9 kg (17 lb 8 oz), and for a female, it’s about 7.3 kg (16 lb 1 oz). Therefore, 8.6 to 9.5 kg would be considered above average and not the anticipated weight for most infants. Choice B rationale: This weight range is below the average for a 6-month-old infant. The average weight at 6 months is significantly higher than 4.1 to 5 kg, as infants are expected to double their birth weight by 5 months of age. Therefore, an infant weighing between 9 to 11 lb at 6 months would be considered underweight. Choice C rationale: This weight range is within the average for a 6-month-old infant. As mentioned, the 50th percentile weights for 6-month-old infants are approximately 7.9 kg for males and 7.3 kg for females. This choice falls within the expected weight gain trajectory where an infant is anticipated to double their birth weight by 5 months and then gain an additional pound or so by 6 months. Choice D rationale: This weight range is significantly above the average for a 6-month-old infant. It is well above the 95th percentile for this age group and would be considered unusual without underlying health conditions that could contribute to such a weight at this age. An infant weighing between 23 to 25 lb at 6 months would be exceptionally rare and likely indicative of an abnormal growth pattern.