How to ensure your baby is safely positioned in the car seat.
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An approved car seat is step one. But how you place your baby in that seat is just as important.
Even with a perfectly installed seat, small mistakes in securing or positioning your baby can have serious consequences in the event of an accident.
Contents
Step by step, place your baby safely in the car seat
Below you walk through the points that matter on every ride: the right size, a correct installation, your baby's posture, the tilt of the seat and snug harness straps.
The right size car seat
Car seats are classified by weight (e.g., Group 0+) or length (e.g., i-Size). So, be sure to check carefully whether the seat is suitable for your baby's height and weight, and for the stage of their life. In how to choose the safest car seat for your baby you'll learn exactly what to consider when making that choice.
Be careful with second-hand car seats
Car seats have a shelf life and can sustain invisible damage after an accident. Avoid using a secondhand seat whose history you don't know unless you trust someone personally and are certain it's accident-free.
The seat is installed correctly
Always consult the instructions for both your car seat and your car. Check that the seat is securely fastened with ISOFIX or the seat belt. The article how do you install a car seat safely provides step-by-step instructions for installing a seat safely and correctly in various cars.
Also mind where the seat goes. Never place a rear-facing car seat on the passenger seat while the airbag is on. Switch the airbag off. If that is not possible, use the back seat. For a forward-facing child, switching off the airbag is not required, but it is safer. Otherwise slide the passenger seat as far back as it goes. Side airbags do no harm. For a baby, the back seat is the safest place anyway.
Rear-facing is safest
With an i-Size seat (R129), your baby must travel rear-facing until at least 15 months. With an older R44 seat, rear-facing applies until at least 9 kg, and preferably 13 kg. Dutch law requires children under 1.35 metres to sit in an approved seat. Rear-facing toddler seats usually go up to about 3 or 4 years, around 105 cm. Extended rear-facing seats go up to about 6 or 7 years and around 125 cm, with a 25 kg maximum.
Sitting rear-facing ensures that the forces of a collision are better distributed across the entire body, instead of the vulnerable neck taking the full impact.
Maintain the correct posture
Your baby should be in a position that supports their head well and prevents their chin from dropping onto their chest. Newborns, in particular, have little neck tension and can't yet hold their heads up on their own.
That's why most baby seats have a natural, reclined position that supports the correct posture: slightly reclined, so the body rests properly and the airways remain clear. If your baby sits too upright, their head can tilt forward. This bends the neck and can restrict airflow. This is often not immediately apparent, but it can be dangerous.
Check the tilt of the seat
The car seat's tilt determines how much your baby sits or lies at an angle. If the angle is incorrect, their head can fall forward.
Many seats have a tilt indicator, such as a water bubble, colored area, or marker line. This allows you to easily check whether the tilt is correct.
When should you check or adjust the tilt?
When first installing the seat
As your baby grows and the sitting position changes
If you see the head drooping forward, especially during sleep
When you place the seat in another car (seats vary by model)
How do you adjust the tilt safely?
Read the seat's manual. Each brand works differently. Follow the manufacturer's instructions carefully.
Check if the seat has a reclining position. Many infant car seats and swivel models have a lever or knob to adjust the angle.
Use the tilt indicator. If the water bubble or color patch isn't in the correct area, adjust the angle or use a solution approved by the manufacturer.
Use only approved accessories. Some manufacturers offer wedges to correct the angle of a steep car seat. Do not use towels, blankets, or other loose materials under the seat. These are unsafe.
Also pay attention to the shape of your car seat. Back seats may have a different angle than you expect. If the seat is too upright:
Try a different seat in the car
Use an approved tilt wedge (only if permitted)
Or choose a seat with an adjustable base, which allows you to adjust the angle on the car seat
Harness straps: tight, correct and comfortable
The harness straps of a car seat should be secure enough to keep your baby safely in place, but also remain comfortable.
In the event of a collision, there should be no slack that could cause your baby to be thrown forward or to the side.
The harness straps should lie flat and not be twisted.
They should fit neatly over the shoulders and fit well against the body.
The hip straps should lie low across the pelvis, not over the tummy. The buckle sits between the legs.
No more than one finger, about 1 cm, should fit between the harness strap and the collarbone.
Harness height at the shoulders. The shoulder straps should pass through the seat at the height of your baby's shoulders, not far above or below them. In a rear-facing seat, level with the shoulders or just below is the safest setting. The manual for that seat is what counts. Adjust the harness in good time as your baby grows.
Many parents do tighten their harness straps, but wonder if it's enough. Here's something to remember:
A car seat only really protects if the harness straps fit snugly
Loose may feel soft and sweet, but tight is safe.
The pinch test
Not sure if you're doing it right? The pinch test is a simple way to check if the car seat harness straps are tight enough and therefore truly safe.
Place your baby properly in the seat and fasten the harness straps according to the instructions.
Tighten the harness straps until they fit snugly against your baby's body.
Using your thumb and index finger, try to grasp a fold in the shoulder area of the harness strap, just above the collarbone.
Can you squeeze a crease? Then the harness straps are still too loose. Tighten them a bit. Can't squeeze a crease? Then your baby is safely secured.
This test is especially useful because the feeling of "tight enough" can sometimes be difficult to judge.
No thick coats or snowsuits under the harness
One of the most common mistakes is strapping your baby into a thick coat or footmuff. This extra layer between your baby and the harness straps can cause the harness straps to be loose, even if it seems fine at first glance.
What you should do instead: always buckle your baby in first, without a coat or thick clothing. Then, place a blanket over the harness straps to keep your baby warm. There are also special car seat foot muffs that are safe, as long as they don't create an extra layer between your baby and the harness straps. This way, your child stays warm and well-protected, without compromising safety during a ride.
Beware of overheating
In winter, thick coats are a problem, but in summer, overheating can occur. In warm weather, make sure your baby isn't too warm, use sunshades to protect against direct sunlight, and check that the seat fabric hasn't become hot.
Use only approved accessories
Extra cushions, inserts, or stuffed animals may seem useful or comfortable, but they can disrupt the seat's functionality. They can prevent the harness straps from fitting properly or reduce protection in a crash. Therefore, only use accessories that are included with the seat or that are explicitly approved by the manufacturer.
The infant insert that comes with the seat does belong in it while your baby is small. Use it for as long as the manual says, and take it out after that. An insert or cushion you buy separately does not belong in the seat, because it was never tested with it.
Four more things to watch for
These points come up less often, but they matter just as much.
Never leave a child alone in the car. Not even briefly, and not with a window left open.
Never put the carrier on a table or a kitchen counter. A baby can push off and tip it over. On the floor it stands safely.
Has the car been in a crash? Replace the car seat, even if you see no damage on the outside.
A car seat has a shelf life. Plastic ages. Check the production date on the shell and do not use it longer than the manufacturer states, usually six to ten years.
Frequently asked questions
How do I know when my baby has outgrown the seat?
Your baby has outgrown the seat once the head rises above the top edge of the shell. It is also time for a larger seat when you can no longer set the harness straps at the right height. The feet may rest against the back seat, that is fine.
My baby cries in the car seat. Is that unsafe?
Not necessarily. Some babies need time to get used to the position. Always check that everything is fastened correctly. Crying can also come from hunger, tiredness or heat.
How often should I check the harness?
Every ride. Harness straps can work loose through daily use. A fixed checking routine takes little time and brings a lot of calm.
How long can my baby sit in a car seat?
There is sometimes confusion about how long a baby can safely sit in a car seat. The Dutch JGZ guideline keeps to these limits:
No more than 1 hour at a stretch: in the car seat.
No more than 2 hours a day in total: across all seats together, including the bouncer.
In the car only: do not use the infant carrier for naps at home.
How tight should a car seat harness be?
The harness straps should lie snugly against the body. No more than one finger, about 1 cm, should fit between the harness strap and the collarbone. The pinch test is an easy way to check this.
What is the pinch test?
In the pinch test you try to grasp a fold in the harness strap at the shoulder. If you can, the harness is still too loose. If you cannot grasp a fold, your baby is safely secured.
Can my baby wear a winter coat in the car seat?
No. Thick coats create slack between the baby and the harness. In a crash the coat is compressed, so the strap suddenly sits far too loose. Always buckle your baby in without a coat and lay a blanket over the harness afterwards.
How do I know my baby is lying properly in the infant carrier?
The head should be well supported and the chin should not drop onto the chest. Always check the seat's tilt indicator.
The safety of your baby in the car is not only about having the right seat, but also about repetition.
Every ride, a quick check: are the harness straps flat, are they tight enough, is your baby not wearing a thick coat, is their head straight, and is the seat securely fastened? It only takes a few seconds, but it makes a world of difference.
Love,
Bobby
Sources
Written by Bobby, maternity nurse at Bobby Kraamzorg. Last updated: September 2026.