SIDS Risk by Age | When Are Babies Most Vulnerable?

As a new parent, you’ve probably been bombarded with all sorts of advice, tips, and “helpful hints” about how to care for your baby. And sure, while most of it is well-meant, it can be pretty time-consuming parsing out the genuinely practicaltidbits from the heaps of useless (or downright superstitious) information.

No, rubbing your baby’s head won’t stimulate hair follicle growth, and believe it or not, a red thread isn’t likely to cure your tot’s hiccups.

But if there’s any topic we’d consider essential reading for all parents — especially during the first year, it’s sudden infant death syndrome (or SIDS). An uncomfortable and upsetting area to research, yes — let’s face it, it’s every parent's worst nightmare — but the good news is it’s very rare. There are also many things you can do to reduce the risk.

Below, we’ll cover SIDS risks, preventative methods, and all the age-related factors involved.

Written by Elvie Editorial TeamPublished on 17th January 2025

Reviewed by Rosey Davidson

Sleep Consultant, founder and CEO of Just Chill Baby Sleep

What is SIDS?

Sudden infant death syndrome (SIDS) refers to the sudden, unexplained death of an otherwise healthy baby, typically (but not always) during sleep. It’s often referred to as ‘crib death’ because it tends to happen when babies are left unattended in their sleeping environments, but SIDS can happen anywhere.

SIDS happens most often in babies under 6 months of age, with the peak risk occurring between 1 and 4 months. From 6 months onward, the risk of SIDS drops significantly.

How common is SIDS?

As we mentioned up top, SIDS is very rare, affecting around 200 babies every year. The latest available data shows that 0.027% of live births are affected by SIDS in the UK, with this figure remaining relatively stable since 2014. While incredibly rare, however, it’s still vital to follow safe sleep practices to keep the risk of SIDS as low as possible.

Do we know the exact cause of SIDS?

Frustratingly, no — the exact cause of SIDS is unknown. Despite decades of research, no single factor has been pinpointed.

But what we do know is that babies who experience SIDS often have other issues with how their brain controls automatic functions like breathing and heart rate. The most popular theory behind SIDS is called the Triple Risk Hypothesis. This proposes that 3 factors increase the risk of a baby suffering from SIDS:

An underlying abnormality or immaturity in the baby’s automatic functions.
The baby’s age, with increased risk during the first few months of life.
Environmental factors, such as stomach sleeping, overheating, or obstructions to the nose or mouth, such as from a loose blanket.

It’s also worth noting that up to 10% of SIDS deaths are due to irregular heartbeats, and some SIDS cases may have their root in an immune response resulting from an infection. Some cases have even been linked to seizures.

What are the SIDS risk factors?

You’ve probably heard that there are a lot of factors that can influence SIDS risk, and while it’s not something anyone wants to obsess over, knowing the key risk factors can help you make informed choices. Here are some of the big ones to keep in mind:

Sleep position: Babies who sleep on their stomachs or sides are at a higher risk. More on that in a second, but bottom line: back is best.
Sleep environment: Think of the crib as your baby’s “sleep zone”. The fewer hazards, the better — no pillows, blankets, or stuffed animals (no matter how cute they look).
Parental smoking: Babies whose parents smoke are more at risk. This includes smoking during pregnancy or around the baby after birth.
Prematurity or low birth weight: Babies who were born prematurely or with a low birth weight are at a slightly higher risk of SIDS. Their bodies are still working on developing all the systems they need, including the ones that regulate sleep and breathing.
Overheating: Babies can’t regulate their body temperature as well as adults, so it’s essential to make sure they’re dressed appropriately (avoiding excessive layers) and the room is set to a comfortable temperature.

Why is stomach sleeping dangerous?

You might have heard that “back is best” when it comes to sleeping, and there’s a very good reason for that. Stomach sleeping significantly increases the risk of SIDS.

When babies sleep on their stomachs, their airways can get blocked more easily. Plus, they’re at a higher risk of rebreathing their own exhaled air, which can lower the oxygen level in their blood and mess with their breathing.

On top of that, when babies sleep on their stomachs, it’s harder for them to lift their heads or turn them if they’re uncomfortable or if their breathing is restricted. Since babies' muscles and motor skills are still developing, they don’t have the ability to adjust their position as quickly as older children or adults.

So, to keep it simple: always place your baby on their back to sleep.

What age are babies most vulnerable to SIDS?

More than 9 in 10 SIDS-related deaths occur in the first 6 months, with babies most at risk between 1-4 months old.

The good news is, the risk of SIDS drops significantly after 6 months, and reduces further after 8 months. By the time your baby reaches their first birthday, the risk of SIDS is much lower. However, it’s important to continue with safe sleep practices to keep your little one as safe as possible.

Here’s a rough breakdown of SIDS risk by age:

0-1 months: Low risk. SIDS is very uncommon during the first month of life.
1-4 months: Highest risk. The majority of SIDS cases occur between 1 and 4 months, making it the most high-risk period.
4-6 months: Significant risk. While SIDS cases are rarer after 4 months, the risk remains fairly high for the first 6 months of your baby’s life.
6-8 months: Reduced risk. Fewer than 10% of SIDS cases occur after 6 months, so the risk is much lower at this stage.
8-12 months: Low risk. SIDS is very rare after 8 months, but you should still follow safe sleep guidelines to ensure your baby is safe while snoozing.

How to reduce the risk of SIDS

So, with all of the above in mind — how do we prevent SIDS and keep our babies as safe as can be while they’re snoozin’? Here are some essential guidelines that experts recommend:

Put them on their back: Always lay your baby down on their back to sleep (no tummy sleeping), even during naps.
Use a firm, flat mattress: Your baby should sleep on a firm, flat surface with no soft bedding, pillows, or soft toys.
Avoid smoking: You should never smoke during pregnancy or around your baby, as this can dramatically increase the risk of SIDS. The same applies to anyone holding or caring for your little one.
Keep baby cool: Dress your baby in light layers and keep the room temperature between 16-20°C. Adjust their layers accordingly if they feel too hot or too cold.
Consider room-sharing, not bed-sharing: It’s recommended that babies sleep in the same room as you (but not in your bed) for at least the first six months. This helps with monitoring while still keeping them safe.
Breastfeed where possible: If you’re able to breastfeed, this has been shown to lower the risk of SIDS.

By following these tips, you can help reduce the risk of SIDS and give your baby the safest sleep environment possible.

Does room sharing help reduce the risk of SIDS?

Room-sharing can significantly reduce the risk of SIDS, and this is backed by the advice of the Lullaby Trust — it’s recommended that babies sleep in their parents’ room for at least the first 6 months.

Sleeping in the same room as your baby makes it much easier to monitor them during the night and respond like lightning if you notice anything unusual. A bassinet or a crib next to your bed for the first 6 months is the safest place for your tot to sleep.

We understand, SIDS is a scary topic — but forewarned is forearmed. By following all of the expert-approved advice above, you’ll reduce the likelihood of SIDS and ensure your tot’s snoozing sessions are as safe as possible.

Reviewed by Rosey Davidson, Sleep Consultant, founder & CEO, in December 2024.