The World Health Organisation (WHO) defines low birth weight as a birth weight below 2,500 grams, irrespective of gestational age. This cut-off is based on epidemiological observations about the increased risk of death of infant. The number of low birth weight is then expressed as a percentage of total live births. The majority of the data comes from birth registers. However, data for the Netherlands and Turkey comes from a national health interview survey.
The infant mortality rate is the annual number of deaths of children under on year of age per 1,000 live births.