small for dates

Last reviewed 01/2018

The terms small for dates or light for dates are used to describe infants weighing less than the tenth centile for their gestation (although other definitions are also available - see below). Note, it is not the third centile that is important here, which can lead to confusion with definitions later in life such as short stature.

The term 'small for gestational age' is nearly, but not precisely synonymous with intrauterine growth retardation.

NICE note that:

• various thresholds for height and weight at birth are used to define 'small for gestational age', the three most commonly used being:
  • a height at birth that is 2 standard deviations or more below the population average, or
  • a weight at birth that is 2 standard deviations or more below the population average, or
  • a weight at birth below the 10th percentile
• in addition to accurate measurements of a newborn's weight, length and head circumference, the diagnosis of small for gestational age requires accurate assessment of gestational age and valid data from a reference population
• the international consensus definition of 'small for gestational age' is a length or weight at birth that is 2 standard deviations below ( <2 SD) the population average for birth or weight
• children classified as born small for gestational age may have concurrent diagnoses such as familial short stature, Turner syndrome, or growth hormone deficiency
• approximately 10% of children born small for gestational age do not reach the normal height range
  • those whose growth has not caught up by 4 years of age are candidates for treatment with growth hormone (1)

Reference:

• 1) NICE (May 2010). Human growth hormone (somatropin) for the treatment of growth failure in children