What causes SIDS, and why mention it with pregnancy?
Sudden Unexplained Infant Deaths (SUIDs) of infants under a year old occur unpredictably and don’t have an obvious cause. Of around 200 such deaths in the UK every year, around 80% are classified as SIDS – Sudden Infant Death Syndrome (also know as cot death). These are the deaths that can’t later be explained by suffocation, infections, or genetic disorders, even after autopsy.
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| Baby by Beth [CC BY 2.0], via Flickr |
But what does this have to do with pregnancy?
Because SIDS happens to very little babies, many of the risk factors are linked to their mother’s health and what happens before and when they’re born.
Not all of them, of course.
The most commonly cited risk is sleeping position: babies on their backs are less likely to suffer stress complications, like restricted breathing or bedding entanglement, than babies placed on their fronts, sides, or co-sleeping.
There could also be a seasonal component, since more SIDS deaths occur in winter. However, this could instead be because parents use more bedding or babies are more likely to get sick.
And there are genetic factors. For example, boys are more likely to suffer from SIDS; one study cited a 50% male excess in SIDS per 1000 live births of each sex[1]. There may be a racial component too (although it’s not clear from the literature whether this has been disentangled from socioeconomic components). Or inherited defects could play a part, such as in channelopathies, ion channels related to the contraction of the heart, which may explain 10-20% of SIDS[2].
During pregnancy, maternal health is a key indicator for SIDS risk. Mums younger than 20, who smoke or take drugs, or get poor prenatal care are more likely to have babies that suffer from SIDS[3]. They’re also more likely to have babies born prematurely (increasing their risk x 4) or underweight (increasing their risk by x 5.7 for 1000–1499 g babies versus 3500–3999 g babies)[4]. An elevated risk is even seen in full term babies born before 39 weeks.
