A 9-month-old's growth chart shows consistent tracking at the 50th percentile for both length and weight for the first 6 months, then a progressive drop to the 10th percentile for weight while length remains near the 50th percentile. Which of the following is the most likely explanation requiring prioritized evaluation?

• A. The infant is experiencing a benign hormonal surge that permanently lowers weight percentile and will resolve without any assessment or change in feeding
• B. This is normal variability; intervention is unnecessary because weight percentiles commonly drop by 40 percentile points without consequence
• C. A genetic syndrome that always presents at 9 months with isolated weight loss but preserved length; therefore, no nutritional assessment should be done
• D. A nutritional problem (insufficient caloric intake or malabsorption) or illness causing weight faltering; requires immediate nutrition assessment and medical evaluation

Answer: (D)