What is a preterm infant?

The definition, incidence and implication of preterm and low birthweight infants in the UK

The term ‘preterm’ applies to infants born early, i.e. before 37 weeks gestation
Infants who are born preterm tend to weigh much less than term infants and fall into one of the categories below:

Terminology	Description
Low birthweight (LBW)	Birthweight < 2.5 kg (5.5 lbs)
Very low birthweight (VLBW)	Birthweight between 1 kg (2.2 lbs) and 1.5 kg (3.3 lbs)
Extremely Low birthweight (ELBW)	Birthweight < 1 kg (2.2 lbs)

A significant proportion of an infant’s weight gain occurs between weeks 36 and 40 of pregnancy and a preterm infant will need to catch up on this missed weight gain. This is why feeding is so important for these infants.

The UK has the highest rate of preterm births in Western Europe.¹ This is thought to be partly due to the increase in maternal obesity² and the older age of the mother in the UK³, both of which are linked with an increased risk of the likelihood of pre-eclampsia
About 50,000 infants are born preterm in the UK each year^2-4
94% of all singleton births below 28 weeks are very low birthweight (under 1.5 kg)⁵
97% of infants born weighing 0.5-1.5 kg can experience ‘growth failure’ at 36 weeks corrected age⁶
The rate of preterm births has increased in many locations: this is mainly due to the increasing preterm delivery of artificially conceived multiple pregnancies⁷
Improvements in perinatal and neonatal care have increased survival of preterm infants. In the period 1995-2000, 50% of the babies born at 22 weeks survived and 81% of those born at 24 weeks survived⁸
Because mortality rates have fallen, the focus for perinatal interventions is to reduce long term morbidity, especially abnormal brain development. Nutrition plays an important role in this

References

M J Saurel-Cubizolles, J Zeitlin, N Lelong, E Papiernik, G C Di Renzo, G Bréart. Employment, working conditions, and preterm birth: results from the Europop case-control survey. J Epidemiol Comm Health 2004;58:395-401.
NHS Maternity Statistics, England: 2003-2004.
Registrar General Annual Report 2004 – Section 3 Births. Northern Ireland Statistics and Research Agency.
Statistics library (Vital Events References Tables). General Registrar Office for Scotland. Crown Copyright 2006
Office for National Statistics. News release 24 May 2007.
Casey PH. Growth of low birthweight preterm children. Semin Perinatol 2008; 32: 20-27.
Goldenberg RL et al. Epidemiology and causes of preterm birth. Lancet 2008; 371(9606): 75-84.
Kate C et al. The EPICure Study: Outcomes to Discharge From Hospital or Infants Born at the Threshold of Viability, Pediatrics 2000; 106 (4): 659-671.

M J Saurel-Cubizolles, J Zeitlin, N Lelong, E Papiernik, G C Di Renzo, G Bréart. Employment, working conditions, and preterm birth: results from the Europop case-control survey. J Epidemiol Comm Health 2004;58:395-401.
NHS Maternity Statistics, England: 2003-2004.
Registrar General Annual Report 2004 – Section 3 Births. Northern Ireland Statistics and Research Agency.
Statistics library (Vital Events References Tables). General Registrar Office for Scotland. Crown Copyright 2006
Office for National Statistics. News release 24 May 2007.
Casey PH. Growth of low birthweight preterm children. Semin Perinatol 2008; 32: 20-27.
Goldenberg RL et al. Epidemiology and causes of preterm birth. Lancet 2008; 371(9606): 75-84.
Kate C et al. The EPICure Study: Outcomes to Discharge From Hospital or Infants Born at the Threshold of Viability, Pediatrics 2000; 106 (4): 659-671.