1. HEALTH STATUS 1.9. Infant health: low birth weight

Low birth weight – defined here as newborns weigh- motherhood (Ohmi et al., 2001). Despite the increase ing less than 2 500 grams – is an important indicator in low birth weight babies, Japanese medical care for of infant health because of the close relationship newborns has been particularly successful in reducing between birth weight and infant morbidity and infant mortality. mortality. There are two categories of low birth weight Figure 1.9.4 shows some correlation between the babies: those occurring as a result of restricted foetal percentage of low birth weight infants and infant growth and those resulting from pre-term birth. Low mortality rates. In general, countries reporting a low birth weight infants have a greater risk of poor health proportion of low birth weight infants also report or death, require a longer period of hospitalisation relatively low infant mortality rates. This is the case after birth, and are more likely to develop significant for instance for the Nordic countries. Japan, however, disabilities (UNICEF and WHO, 2004). Risk factors for is an exception, reporting the highest proportion of low birth weight include being an adolescent mother, low birth weight infants but one of the lowest infant having a previous history of low weight births, harm- mortality rates. ful behaviours such as smoking, excessive alcohol Comparisons of different population groups within consumption and poor nutrition, a low Body Mass countries show that the proportion of low birth weight Index, a background of low parental socio-economic infants is also be influenced by differences in education, status or minority race, as well as having in-vitro income and associated living conditions. In the fertilisation treatment (IHE, 2008). United States, marked differences between groups in In 2007, the Nordic countries – including Iceland, the proportion of low birth weight infants have been Sweden and Finland – reported the smallest propor- observed, with black infants having a rate almost double tions of low weight births, with less than 4.5% of live that of white infants (CDC, 2009a). Similar differences births defined as low birth weight. Turkey, Japan, have also been observed among the indigenous and Greece, the United States and Hungary are at the non-indigenous populations in Australia (Laws and other end of the scale, with rates of low birth weight Hilder, 2008) and Mexico, reflecting the disadvantaged infants above 8% (Figure 1.9.1). These figures compare living conditions of many of these mothers. with an overall OECD average of 6.8%. Since 1980 the prevalence of low birth weight infants has increased in a number of OECD countries (Figure 1.9.2). There may be several reasons for this rise. First, the number of multiple births, with the Definition and deviations increased risks of pre-term births and low birth weight, has risen steadily, partly as a result of the rise Low birth weight is defined by the World Health in fertility treatments. Other factors which may have Organisation (WHO) as the weight of an infant at influenced the rise in low birth weight are older age at birth of less than 2 500 grams (5.5 pounds) irre- childbearing and increases in the use of delivery man- spective of the gestational age of the infant. This agement techniques such as induction of labour and is based on epidemiological observations regard- caesarean delivery. ing the increased risk of death to the infant and serves for international comparative health Japan, Portugal and Spain, historically among a group statistics. The number of low weight births is of countries with a low proportion of low birth weight, then expressed as a percentage of total live have seen great increases in the past 25 years. As a births. result, the proportion of low birth weight babies in these countries is now above the OECD average The majority of the data comes from birth regis- (Figure 1.9.3). In the case of Japan, a number of risk ters, however for Mexico the source is a national factors have been cited as contributing to this health interview survey. A small number of increase, including the rising prevalence in smoking countries supply data for selected regions or among younger women from the 1970s onwards hospital sectors only. together with a significant move towards later

32 HEALTH AT A GLANCE 2009: OECD INDICATORS © OECD 2009 1. HEALTH STATUS

1.9. Infant health: low birth weight

1.9.1 Low birth weight infants, 1.9.2 Change in proportion of low birth 2007 (or latest year available) weight infants, 1980-2007

3.8 Iceland 11.8 4.1 Sweden -2.4 4.3 Finland 10.3 4.6 Luxembourg -27.0 4.7 Korea n.a. 5.0 Ireland 25.0 5.1 Norway 34.2 5.9 New Zealand 1.7 6.0 Poland -21.1 6.1 Canada 5.2 6.2 Netherlands n.a. 6.4 Australia 14.3 6.4 Switzerland 25.5 6.7 Denmark 15.5 6.7 Italy 19.6 6.8 OECD 26.0 6.8 France 30.8 6.9 Germany 25.5 7.1 United Kingdom 6.0 7.2 Austria 26.3 7.4 Czech Republic 25.4 7.5 Slovak Republic 27.1 7.6 Spain 171.4 7.8 Mexico n.a. 7.8 Portugal 69.6 7.9 Belgium 41.1 8.2 Hungary -21.2 8.3 United States 22.1 9.0 Greece 52.5 9.7 Japan 86.5 11.3 Turkey (2003) n.a. 15 10 5 0 -50 0 50 100 150 200 Percentage of newborns weighing less than 2 500 g % change over period

1.9.3 Trends in low birth weight infants, 1.9.4 Low birth weight and infant mortality, selected OECD countries, 1980-2007 2007 (or latest year available)

Japan Spain Infant mortality (deaths per 1 000 live births) 21 Sweden OECD R2 = 0.32 TUR Percentage of newborns weighing less than 2 500 g 10

MEX

14 8

6

7 POL SVK USA HUN CAN 4 KOR NZL GBR NOR FIN GRC SWE LUX CZE PRT JPN ISL IRL

2 0 1980 1985 1990 1995 2000 2005 04812 Low birth weight (%)

Source: OECD Health Data 2009. 1 2 http://dx.doi.org/10.1787/717583038273

HEALTH AT A GLANCE 2009: OECD INDICATORS © OECD 2009 33 From: Health at a Glance 2009 OECD Indicators

Access the complete publication at: https://doi.org/10.1787/health_glance-2009-en

Please cite this chapter as:

OECD (2009), “Infant health: low birth weight”, in Health at a Glance 2009: OECD Indicators, OECD Publishing, Paris.

DOI: https://doi.org/10.1787/health_glance-2009-11-en

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