Sudden unexpected death in infancy (SUDI) is a leading cause of preventable death in New Zealand babies. Since the 1980s, the number of SUDI deaths reduced from 250 per year (over 4.4 per 1,000 live births) to 44 deaths in 2015 (0.71 per 1000 live births). Significant reduction in the rate of SUDI has occurred over the past three plus decades, but too many of our babies are still dying. It is estimated that up to 37 of the 44 deaths in 2015 could have been prevented (Mitchell et al 2017).

In the 1980s, New Zealand had one of the highest Sudden Infant Death Syndrome (SIDS) rates (over 4.4 per 1,000 live births) in the Western world. The New Zealand Cot Death Study (1987-1990) identified three key risk factors: prone (front) sleep position, maternal smoking and lack of breastfeeding (Mitchell, Scragg et al. 1991). A year later, bed sharing was also identified as a risk factor (Mitchell, Taylor et al. 1993) and later this was found to be particularly so where mothers smoked in pregnancy, (Carpenter, Irgens et al. 2004) became excessively tired or used alcohol (Blair, Fleming et al. 1999) or had used sedative drugs (Kahn and Blum 1982).

In the late 1990s the SIDS prevention advice was updated on the basis of research findings, and recommend that babies sleep on their backs only and not on their sides or fronts. Researchers considered that uptake of the new advice contributed to the gradual decline in SIDS rates up until 2000 (Mitchell et al 2007). These SUDI prevention public health messages, first promoted in the 1990s, remain applicable today (Mitchell et al 2017). A safe sleep and smokefree environment is vital for every baby and this message should be reinforced and supported through a mix of universal and tailored SUDI prevention services.

More recently, the combination of bed sharing and maternal smoking in pregnancy has been established as extremely hazardous to babies, leading to a 32-fold increased risk of SUDI, compared with babies not exposed to either risk factor (Mitchell et al 2017). It can be very difficult for pregnant women and mothers to quit smoking, especially if their friends and other members of their household are smokers. As such, tailored, supportive and appropriate smoking cessation services are required. Similarly, widespread availability of safe sleep devices will help support a safe sleep environment for baby, wherever they may be.

New Zealand has a particular challenge in that, the greater proportion of deaths are in the Māori community and are known to be drawn from those infants who bed-share with another person (Hutchison, Rea et al. 2011) and where the mother smoked in pregnancy, a behaviour known to be high in the Māori community (Tipene-Leach, Hutchison et al. 2010). The Pasifika community also has a high rate is recently found to be not decreasing over time, innovative approaches to addressing the inequitable SUDI rates is needed.

Commonly Used Terms

Bed sharing is when two or more individuals (infant and another individual including other children) share a surface, such as a bed, or other surface when they are asleep (either intentionally or unintentionally).

Safe sleep environment/surface/device is when a baby is placed on their own sleeping surface. The most common form of safe sleep environment is a bassinet, or cot, however more recently this has also included a wahakura (flax woven baby bed), BabyStart Box and the Pepi-pod these are designed to be put on the parental bed or another firm surface before placing the baby in them for sleep.

Sudden infant death syndrome (SIDS) is the sudden death of an infant (under one year of age) that cannot be explained after a thorough examination is conducted, including an autopsy, examination of the death scene and review of the clinical history.

Sudden unexpected death in infancy (SUDI) is an umbrella term that describes the death of an infant that was not anticipated, within the first year of life. Deaths categorised as SUDI contains a spectrum of cases from those that are unexplained following full investigation (SIDS, as above) to fully explained cases (explained SUDI). Between them are cases where a pathologist or coroner cannot be certain as to whether the death is explained or not; these are often labelled ‘unascertained’. Previously these deaths were known as ‘cot deaths’ and then people began to use the term SIDS. Now the preferred term is SUDI, although this umbrella term includes the group of unexplained SIDS deaths, as noted above.


  1. Mitchell EA, Thompson J, Zuccollo J, MacFarlane M, Taylor B, Elder D, Stewart A, Percival T, Baker N, McDonald G, Lawton B, Schlaud M, Fleming P. The Combination of bed eharing and maternal smoking leads to a greatly increased risk of sudden unexpected death in infancy: The NZ SUDI Nationwide Case Control Study. NZ Med J 2017.
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