Professor Ed Mitchell
SUDI Academic Expert
Auckland University

Ed Mitchell qualified at St George’s Hospital Medical School in London and has worked in the UK, Zambia and New Zealand.

He was the Cure Kids Professor of Child Health Research at the University of Auckland from 2001 to 2015 and is now a Professorial Research Fellow. He has published over 400 original papers, particularly on the epidemiology of sudden infant death syndrome (SIDS). He was awarded a Doctor of Science for his work on “The Epidemiology and Prevention of SIDS” by the University of London. He has received several awards for his landmark studies of SIDS and in 2009 was made a fellow of the Royal Society of New Zealand.

A. Many studies have shown that sleeping with baby on the same sleeping surface, usually a mattress, increases the risk of sudden unexpected death in infancy (SUDI). Indeed over 50% of SUDI cases now occur in a bed sharing situation. There are certain factors that increase the risk further. These include the first 3-4 months of life, whether or not the mother smoked in pregnancy, whether she took drugs or alcohol before sleeping with the baby or was excessively tired and whether the baby was vulnerable, such as low birthweight or preterm. Even without these additional risks bed sharing increases the risk 3-fold, so our advice is “For the first six months, the safest place for baby to sleep is in a cot in the parent’s bedroom.”

A. We believe the mechanism is accidental suffocation. The nose of the baby is soft and can easily be compressed. Also the jaw can be pushed back and occlude the airway. A healthy baby will arouse (wake up) and wriggle, but if mother has taken drugs or alcohol she won’t be responsive to this. Also if the baby has been exposed to smoking when in the womb, the arousal mechanisms are blunted, and the baby may not wake up.

A. Babies will often fall asleep in a car seat when travelling. Not surprisingly it is tempting to leave the baby asleep in the capsule when they arrive home. But is it safe? Studies of babies in car seats show that their head may flop forward and cause partial airway obstruction and hypoxia (low oxygen levels). This will briefly wake baby up (micro-arousals). Despite these concerns, SUDI in a car seat is rare. In the 3-year Nationwide SUDI Study there was only 1 death (out of 137) that occurred in a car seat. In comparison there were 7 control (living) babies (out of 249) in a car seat during the comparison sleep. This suggests it isn’t dangerous in healthy babies, but I would be concerned about repeated hypoxia in low tone babies, such as those with Down syndrome.

A. Questions relating to type and amount of baby clothing are frequent. In the original New Zealand Cot Death Study (1987-1990) baby hats (e.g. beanies and bonnets) were used in 8.3% of cases and 5.2% of controls. In the Nationwide SUDI Study hats were used by 4.8% of cases and 3.9% of controls. These differences are small and not statistically significant.

In infants the surface area of the head and neck is 20% of their total body area (compared with just 9% in adults). Heat loss can be considerable, so in cold conditions a hat will reduce this. This may prevent the baby getting cold and uncomfortable. But it doesn’t affect the risk of SUDI.

Head covering increases the risk of SUDI, but this does not refer to hats; it refers to baby’s head being covered with blankets. A meta-analysis of 10 studies found the prevalence in cases was 24.6% and 3.2% among controls. This suggests head covering by blankets is a modifiable risk factor associated with SIDS deaths and has led to the UK recommendation to place baby at the foot of the bed (“Feet to foot”). Theoretically this might prevent babies kicking the blankets over their heads, but there isn’t much evidence to support that this happens, which is why we do not emphasise this in New Zealand.

A. Sudden infant death syndrome (SIDS) has been present since antiquity. Indeed it is described in the Old Testament of the Bible: 1 Kings 3:19 ‘‘And this woman’s child died in the night.’’ “Cot death” was well known to pathologists, but not to paediatricians as they never saw them, as the deaths occurred in the home. These deaths were often labelled as pneumonitis (inflammation of the lung). It was not until 1965 that a specific International Classification of Diseases (ICD) code was allocated for SIDS. SIDS is the scientific term for a sudden unexplained infant death. These deaths generally occur during a sleep, and no cause is found despite a detailed examination of the death scene, medical history and thorough autopsy. Nowadays 50+% of deaths occur in a bed sharing context, so using the term “cot death” is inappropriate. The cause of deaths associated with bed sharing may be labelled as accidental asphyxia (i.e. suffocation), SIDS (that is unexplained) or unascertained (often used when the pathologist cannot distinguish between suffocation and SIDS). The trouble is that one pathologist or coroner might call the death SIDS and another accidental asphyxia. Sudden unexpected death in infancy (SUDI) captures all three causes, including unexplained and explained.