Babies Sleeping On The Side: What Happens If They Do And How To Stop It

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Experts recommend that pregnant mothers sleep on their left side to ensure more nutrients flow to the baby. However, parents often wonder about the benefits or risks of babies sleeping on the side.

Babies have different sleeping patterns, and many may prefer to sleep on their sides. Although this trait is harmless in adults, it may cause adverse effects in babies. If babies regularly sleep on their side, they may develop health conditions such as flathead or a tilt in the neck and increase their risk of choking.

This post explains why babies should not sleep on their side, how sleeping on one side can affect their health, when babies can sleep this way, and what to do when they roll to one side in their sleep. It also provides tips to prevent babies from rolling to one side.

Is It Safe To Make The Baby Sleep On One Side?

Do not make the baby sleep on one side as it might lead to certain health conditions as mentioned below:

1. Harlequin color change:

The medical term for harlequin color change is unilateral erythema, and it affects nearly 10% of newborn babies (1). It is usually seen in the first week of birth. In this condition, the sleeping side of the infant’s body turns pink or red with a clear demarcation running through the central axis of the baby’s body. This means the baby’s body will be half red and half normal-colored. The color will change spontaneously when the infant sleeps on the side for hours.

But the condition is completely benign and does not cause any lasting health issues. Switching the position of the baby makes the red color fade away within minutes.

Medical experts do not know the precise reason for this phenomenon, but they suspect it occurs due to the immature blood vessels in the skin. It may also be associated with polycythemia (a dark red baby due to the increased red blood cells in the body). The color indicates a possible accumulation of red blood cells, due to gravity, among the cutaneous blood vessels (blood vessels close to the skin). This could happen due to the immature blood vessels in babies.

Treatment: Harlequin color change is a harmless condition and disappears on its own.

2. Flatheads:

Preventing flatheads in babies sleeping on the side

Image: iStock

The bones of a baby’s skull remain soft and malleable to allow the skull expand at the same rate as the brain. The soft bones naturally pose a risk of developing flatheads. Flathead happens when the baby’s head is placed in a single position repeatedly to the extent that pressure builds up at a single spot on the skull. The bones of the skull at that point sink and go concave or flatten. It is basically a skeletal anomaly but can lead to stunted brain growth due to less cranial space for the brain to expand. This may hamper the baby’s cognitive abilities later in life. The medical term for a flathead is plagiocephaly.

Flatheads also occur if the baby sleeps straight but puts his head to the side, and due to prolonged sleeping on one side (2). A neck condition called torticollis could also lead to flatheads.

A more rare form of plagiocephaly is due to abnormal bone formation in the skull, which has to be surgically corrected.

Treatment: When diagnosed on time, flatheads can be corrected with the use of head braces called baby helmets since the baby’s skull bones are still soft enough to reposition themselves. The head braces are prescribed by the doctor and made by certified medical manufacturers or hospitals.

If the baby’s condition is not severe, then the doctor will simply recommend repositioning your baby’s sleeping side to rectify the flathead (3).

Did you know?
Infants’ skulls are moldable and soft until they are around four months old (4).

3. Torticollis:

Torticollis may occur due to side sleeping

Image: Shutterstock

Torticollis is an abnormal tilting of the neck in one direction due to the severe shortening of the sternocleidomastoid muscle that connects the lateral side of the head to the clavicle. Torticollis can occur due to several reasons, one of them being the poor positioning of the baby while sleeping (4).

Since babies’ muscles are tender and growing, the sternocleidomastoid muscle may shorten due to repeated sleeping on the side or turning the head to the side while sleeping on the back. This condition will not just affect the growth of the muscle but also cause abnormal bone growth.

Babies with torticollis turn their head side-to-side while sleeping.

Treatment: Physical therapy will help release the stiffness in the muscles (3). The doctor may recommend wearing a recovery harness that is wrapped around the baby’s body with a soft pad near the neck. This pad pushes the head in the opposite direction, gradually bringing back the neck to its normal position. The doctor will also give you some safe sleeping techniques for the baby’s condition to improve.

4. Risk of choking:

Sleeping on the side creates torsion in the windpipe (trachea) that can make breathing difficult for the baby. Also, it can result in the accumulation of regurgitated food around the tracheal opening, posing a choking hazard. This also happens during tummy sleeping – a position to which your baby may topple during side-sleeping. These positions increase the risk of sudden infant death syndrome (SIDS) (5).

Treatment: Do not allow the infant to sleep on his side to prevent choking and SIDS.

Research finds
Around 3,500 babies in the United States die every year suddenly and unexpectedly while sleeping, mainly due to SIDS (6).

These repercussions, some long-term and some temporary call for the need to prevent your baby from sleeping sideways.

How To Prevent Your Baby From Side-Sleeping?

You can take some easy precautions to prevent your baby from sleeping on his side:

1. Place your baby on the back during sleep time:

Baby sleeping on the back

Image: iStock

The simplest precaution is to place your baby on his back when putting him to sleep in his crib or cradle. Research has proven that the back position is the best way of preventing fatal medical conditions such as SIDS (6). This position also reduces upper respiratory infections.

2. Do not place unnecessary support structures on the bed:

Do not place support structures on the crib or the bed of the baby. These structures could be anything from home pillows to specially-made crib bumpers that have no proven record to provide any benefit or safety to the sleeping baby. Certain support structures like pillows may even cause the baby to roll over to the side in case he moves during his sleep (6).

3. Never use sleep positioners or wedges:

Sleep positioners are not safe for babies. In fact, some are designed to ensure that the baby sleeps on the side while some encourage the baby to sleep on the back. Avoid both such positioners. Sleep positioners have been proven to pose a suffocation hazard (7).

4. Swaddling may increase the risk of roll over:

If you swaddle your baby you automatically increase the risk of him rolling over to the side. This is because swaddling creates a smooth cylindrical surface around the baby that makes it easy for him to roll over. In fact, swaddling could increase the risk of SIDS (8).

5. Keep altering the baby’s sleep positions:

If your baby sleeps on his back, then switch the position of his head every alternate night. For example, if he sleeps on his back with his head rested a bit towards the left side then the next night gently shift his head to the right side. This will help prevent the development of flatheads. Also, put your baby to sleep in a separate crib or cradle in the same room where you sleep. Do not put unnecessary bedding or padding in the crib that will make the baby slip into side-sleeping position.

In the initial months, the babies do not move much. But once their mobility improves, it could be difficult for you to make him sleep on the back. So, for how long should you make an effort to make him sleep straight?

When Can Babies Sleep On Their Side?

Safe age for babies to sleep on the side

Image: iStock

Babies should be made to sleep on his back till they complete 12 months, after which he can sleep on his side (9). By this age, your baby’s esophagus, trachea and overall breathing mechanism are fairly developed. Thus, it is now safe for him to sleep on his side.

What If The Baby Rolls To Side In Sleep?

Putting the sleeping baby on their back

Image: iStock

At around six months of age, your baby could roll over to his tummy or the side from the back position. Rolling over is a natural part of your baby’s development. If your baby rolls over to the tummy or his side on his own, then you can let him sleep in that position (9).

Generally, a baby will get on to the side or stomach sleeping position only when his muscles are strong enough to let him do so. If he can roll over on his own then it is an indicator that the baby has stronger internal organs and is at a lower risk of choking himself during sleep.

However, if your baby rolls over before he reaches six months, then you must put him in the back position again.

Stop swaddling your baby once you find them rolling over in their sleep (8).

Frequently Asked Questions

1. What if the baby is not comfortable sleeping on their back?

If your baby is not comfortable sleeping on the back, try to identify the cause. Check their bedding and the room temperature to ensure they are convenient for your baby. Try to swaddle your baby before bedtime. You may also try placing them on the bed after falling asleep.

2. Is it okay for a newborn to sleep on the back with their head to the side?

No. Sleeping on the side could increase the baby’s risk of developing a flat head. Hence, even if the baby is placed on their back, with the head turned to the side, they might still be at risk of developing a flat head (2).

3. What age does the risk of SIDS reduce?

SIDS is common among babies between one month and twelve months. The risk of SIDS reduces as the baby grows older and learns to gain control of their movements (5).

Babies sleeping on their sides have an increased risk of developing a flathead or suffering from torticollis which results in abnormal tilting of the head. However, if your baby naturally rolls into a side sleeping position, do not change their stance, as it is a part of their development and will not lead to any complications. Making your baby sleep in a sideways position also increases the risk of choking. Remember to make your baby sleep on their backs and keep altering the positions of their heads on alternate days to prevent flatheads.

Infographic: How To Stop Babies From Sleeping On Their Side

Side-sleeping increases the risk of suffocation and other sleep-related problems in babies. Therefore, preventing your baby from side-sleeping when you put them to sleep is necessary. Scroll through the infographic below to learn tips to avoid side-sleeping in your little one.

ways to prevent your baby from side sleeping [infographic]
Illustration: MomJunction Design Team


MomJunction's articles are written after analyzing the research works of expert authors and institutions. Our references consist of resources established by authorities in their respective fields. You can learn more about the authenticity of the information we present in our editorial policy.
  1. Judy Tang et al.; (2010); Harlequin colour change: unilateral erythema in a newborn.
  2. Paediatr Child Health; (2001); Preventing flat heads in babies who sleep on their backs.
  3. Flat Head Syndrome (Positional Plagiocephaly).
  4. Plagiocephaly (Flat Head Syndrome).
  5. Sudden Infant Death Syndrome (SIDS).
  6. How to Keep Your Sleeping Baby Safe: AAP Policy Explained.
  7. Sleep Positioners: A Suffocation Risk.
  8. Swaddling: Is it Safe?
  9. Safe Sleep.

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