Low Birth Weight

3. HEALTH STATUS Infant health: Low birth weight

Low birth weight – defined as newborns weighing less than weight babies between 2009 and 2012 were linked to the 2 500 grams – is an important indicator of infant health economic crisis and its impact on unemployment rates and because of the close relationship between birth weight and lowering family incomes in Greece (Kentikelenis, 2014). In infant morbidity and mortality. There are two categories of 2013, the rate came down to levels observed before the crisis. low birth weight babies: those occurring as a result of Comparisons of different population groups within coun- restricted foetal growth and those resulting from pre-term tries indicate that the proportion of low birth weight birth. Low birth weight infants have a greater risk of poor infants may also be influenced by differences in education health or death, require a longer period of hospitalisation level, income and associated living conditions. In the after birth, and are more likely to develop significant United States, there are marked differences in the proportion disabilities. Risk factors for low birth weight include mater- of low birth weight infants among racial groups, with black nal smoking, excessive alcohol consumption, poor nutri- infants having a rate almost double that of white infants tion, low body mass index, lower socio-economic status, and (13% versus 7% in 2013) (NCHS, 2015). Similar differences having had in-vitro fertilisation treatment and multiple have also been observed among the indigenous and non- births. indigenous populations in Australia, Mexico and New One in 15 babies born in OECD countries in 2013 – or 6.6% of Zealand, often reflecting the disadvantaged living condi- all births – weighed less than 2 500 grams at birth tions of many of these mothers. (Figure 3.16). The proportions of low-weight births were The proportion of low birth weight infants is also generally lowest in Nordic countries (Iceland, Finland, Sweden, higher among women who smoke than for non-smokers. Norway, with the exception of Denmark) and Estonia, with less than 5% of live births defined as low birth weight. Japan, had the highest proportion of low birth weight infants among OECD countries, with rates close to 10%, Definition and comparability followed by Greece, Hungary and Portugal. Low birth weight is defined by the World Health Despite the widespread use of a 2 500 grams limit for low Organization (WHO) as the weight of an infant at birth birth weight, physiological variations in size occur across of less than 2 500 grams (5.5 pounds) irrespective of different countries and population groups, and these need the gestational age of the infant. This threshold is to be taken into account when interpreting differences based on epidemiological observations regarding the (Euro-Peristat, 2013). Some populations may have lower increased risk of death to the infant and serves for than average birth weights than others because of genetic international comparative health statistics. The number differences. of low weight births is expressed as a percentage of In almost all OECD countries, the proportion of low birth total live births. weight infants has increased over the past two decades, mainly due to increases in pre-term births (Euro-Peristat, 2013). There are several reasons for this rise, including a growing number of multiple pregnancies mainly as a result References of the rise in fertility treatment, and a rise in maternal age Delnord, M. et al. (2015), “What Contributes to Disparities (Delnord et al., 2015). Another factor which may explain the in the Preterm Birth Rate in European Countries?”, Cur- rise in low birth weight infants is the increased use of deliv- rent Opinion in Obstetrics and Gynecology, Vol. 27, No. 2, ery management techniques such as induction of labour pp. 133-142, April. and caesarean delivery, which have increased the survival Euro-Peristat (2013), European Perinatal Health Report: The rates of low birth weight babies. Health and Care of Pregnant Women and their Babies in 2010, Korea, Greece, Spain, Portugal and Japan have seen large Luxembourg. increases of low birth weight babies over the past two Kentikelenis, A. (2014), “Greece’s Health Crisis: From decades, although the proportions remain below the OECD Austerity to Denialism”, The Lancet, Vol. 383, No. 9918, average in Korea (Figure 3.17). In Japan, this increase can be pp. 748-753. explained by changes in obstetric interventions, in particu- NCHS – National Center for Health Statistics (2015), Health, lar the greater use of caesarean sections, along with United States, 2014, With Special Feature on Adults Aged changes in maternal socio-demographic and behavioural 55-64, NCHS, Hyattsville, United States. factors (Yorifuji et al., 2012). In Greece, the rise in the proportion of low birth weight babies started in the mid-1990s, Yorifuji, T. et al. (2012), “Trends of Preterm Birth and Low well before the economic crisis, and peaked in 2010. Some Birth Weight in Japan: A One Hospital-Based Study”, researchers have suggested that the high rates of low birth BMC Pregnancy and Childbirth, Vol. 12:162.

60 HEALTH AT A GLANCE 2015 © OECD 2015 3. HEALTH STATUS

Infant health: Low birth weight

3.16. Low birth weight infants, 2013 (or nearest year) % of newborns weighing less than 2 500 g 10 9.6 8.9 8.8 8.7 8.4 8.1 8.0 7.9 7.8

8 7.6 7.5 7.3 7.0 7.0 6.8 6.8 6.7 6.6 6.6 6.6 6.2 6.1 6.0 6.0 6.0 6.0 6 5.8 5.8 5.5 5.5 4.6 4.3 4.3 4.1

4 3.7

Italy Korea Chile Spain Israel Japan IcelandFinlandEstonia Norway MexicoIreland Poland Canada FranceAustria Turkey Greece Sweden Slovenia AustraliaGermany OECD34 Belgium Denmark PortugalHungary Netherlands Switzerland Slovak Rep. Czech Rep. New Zealand Luxembourg United States United Kingdom

Source: OECD Health Statistics 2015, http://dx.doi.org/10.1787/health-data-en. 1 2 http://dx.doi.org/10.1787/888933280794

3.17. Trends in low birth weight infants, selected OECD countries, 1990-2013

Greece Japan Korea Portugal Spain OECD % of newborns weighing less than 2 500 g 10

0 1990 1995 2000 2005 2010

Source: OECD Health Statistics 2015, http://dx.doi.org/10.1787/health-data-en. 1 2 http://dx.doi.org/10.1787/888933280794

Information on data for Israel: http://oe.cd/israel-disclaimer

HEALTH AT A GLANCE 2015 © OECD 2015 61 From: Health at a Glance 2015 OECD Indicators

Access the complete publication at: https://doi.org/10.1787/health_glance-2015-en

Please cite this chapter as:

OECD (2015), “Infant health: Low birth weight”, in Health at a Glance 2015: OECD Indicators, OECD Publishing, Paris.

DOI: https://doi.org/10.1787/health_glance-2015-13-en

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