What indicates that an infant is small for gestational age?

• A. Less than 5th percentile
• B. Less than 10th percentile
• C. Less than 15th percentile
• D. Less than 20th percentile

Answer: (B)

The classification of an infant as small for gestational age (SGA) is typically based on their growth parameters compared to a standard population. The most widely accepted cutoff for defining SGA is an infant whose birth weight is below the 10th percentile for their gestational age. This indicates that the infant is smaller than 90% of infants at the same gestational age, suggesting growth that is less than optimal.

Being below the 5th percentile would indicate a more extreme level of growth restriction, but the threshold for SGA is specifically set at the 10th percentile to capture a broader range of infants who may face potential health challenges. The percentages below 10 and 20 are less commonly recognized thresholds for defining SGA, as they do not align with the standard medical definitions used in perinatal care. Thus, choosing less than 10th percentile as the indicator aligns with established guidelines and clinical practice.