I-Size. New Car Seat Laws and Why Rear Facing is Safer

What is i-Size and Why is Rear Facing Safer?

maxi cosi pearl 2 way

Earlier this year new child car seat laws were introduced in the UK and if you’re like me, I found them seriously confusing. With my daughter due to move out of her newborn car seat, I have been doing quite a lot of research around this subject which I thought I would share.

One of the big things is the introduction of i-Size and extended rear facing car seats. I wrote an article a few weeks back (The Second Child Rear Facing Dilemma), because I couldn’t decide what to do when the time came to move my daughter out of her newborn seat. To move her into her brother’s old forward facing car seat, or to buy a new i-Size seat for her so she could rear face for longer.

Since I have written that article, I have been very lucky in that Maxi-Cosi have sent me a Pearl 2 Way Fix car seat to review, which I will be reviewing on the blog next week and so I can let you know what I think.

However, here is a summary of my research and thoughts on the subject.

Current UK Laws

Children need to be in a car seat until they are 12 years old or 135cm which ever comes soonest.

You can read full details here on the government’s website.

Weight Based Car Seats

This is the old car seat laws which were based on your child’s weight. These laws are still in place and run alongside the new i-Size laws.

  • Children weighing 9kg or less should be in a rear facing car seat.
  • 9-18kg a rear or forward baby facing seat.
  • 15-22kg a rear or forward facing child seat (booster)
  • Over 22kg booster cushion


I-Size is a new type of car seat. It is based on your child’s height instead of weight. But also has additional safety standards too.

I-Size car seats only fit into cars with IsoFix, which means you car will need to have IsoFix fittings in order for you to use them. For obvious reasons, people with older cars without IsoFix will not be able to use i-Size. IsoFix is now compulsory in all new cars. Not all older IsoFix cars are i-Size compliant (you need to check you car before you buy the car seat), but new manufactured cars are now being produced with i-Size fittings.

I-Size and old regulations will be running side by side for a few years, but the laws have changed to increase child safety in cars.

The eventual aim is that i-Size will replace current car seat laws.

Why is i-Size Safer?

  • i-Size seats provide better head and neck protection (I’ve written more on extended rear-facing car seats below).
  • i-Size also provides better side-impact protection because it includes new regulations and testing on safety performance for this type of collision.
  • As i-Size uses IsoFix this is also viewed as safer, because IsoFix prevents car seats from being incorrectly fitted. With anchorage points in a car you attach the car seat to, you do not use the car’s seat belt. This leaves less room for user error.
  • A new third anchorage point for IsoFix which also anchors car seats at the top as well as the bottom has been introduced in newer cars too.

Rear Facing

In i-Size car seats it is mandatory to have your child rear-facing until they are 15 months old.

If you do not have an i-Size car seat and have an older style, weight-based, forward facing car seat for your child, then when they are over 9kg, you can place them forward facing.

Although it is worth stating, that you do not have to buy an i-Size car seat to do extended rear-facing. There are other providers that do them with without IsoFix until your child is 4 years old should you choose to.

Also, the advice is to keep your baby in their newborn seat as long as possible, don’t move them up as soon as they are 9kg. A lot of the newborn car seats go up to 13kg. Your child has only grown out of the seat when their head goes over the top of the car seat or they exceed the weight limit, not when their feet stick out the seat.

Why is Rear Facing Safer?

Babies heads account for 25% of their body weight. Research has shown that in forward facing collisions baby’s necks are not strong enough to support their heads.

At 15 months, your baby’s neck is stronger and more able to cope with forward collision, hence the new laws.

However, in other European countries children are kept rear facing until 4 years old and in the US they are advised to keep children rear-facing until 2 years old.

Rear facing car seats are 5 times safer than forward facing.

In forward facing seats children get flung forwards in a front collision. They get caught by the seat harness which puts pressure on their neck, spine and internal organs. A child’s bones are not fully formed and have not solidified into bone, so they are softer than an adult’s skeleton. In some cases their necks cannot take the force and their rib cages are not strong enough to withhold the pressure. In a very worse case scenario a child’s neck will break or ribs crush and damage their internal organs. In a rear facing seat, the seat absorbs most of the force, not the child and the harness.

In Scandinavian countries they have been rear-facing childs up to 4-5 years old for years and their child fatality in car accidents in significantly lower.

Additionally, The British Medical Journal has recommended children are rear-facing until 4 years old.

*Safety information sourced from: www.rearfacing.co.uk

My Thoughts?

I found all of this research pretty compelling and as a consequence have decided to put my daughter in a rear-facing car seat for as long as possible. Far longer than the recommended 15 months. At least up until 3 if I can. I have concerns about car sickness, because even as an adult I suffer and rear facing makes it ten times worse. Also, how happy she will be rear-facing, but I hope as she doesn’t know any different, she will be fine.

If I hadn’t have been sent the Maxi-Cosi 2-Way Pearl to review (review with my 1 year old daughter and 3.5 year old son to come next week), my husband and I would have purchased one. With this data in hand I would have never of forgiven myself if something happened to my daughter and we had a nasty accident.

What are your thoughts?

*Please note some of this information was provided to me via a press release Maxi-Cosi provided. However, they did not ask me to write this article and all opinions are my own. All other sources have been cited. I am in no way an expert in this area, so please double check before making legal decisions. *

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10 thoughts on “I-Size. New Car Seat Laws and Why Rear Facing is Safer”

  1. I also find all this car seat buiness so confusing. Thankfully my sons old enough that i dont need to worry! linked up from #PicknMix xx

    • You’re lucky then, as you say it is quite confusing. I think more so what to do if you already have a carsears from your first child.

  2. Both my boys are rear-facing, O is almost 4 and still ok rear-facing in his Britax max-way. It’s comfy, he can see out the windows and we can see him with the mirror attached to the headrest in front of him. He’s had no problems rear facing and we’ll do the same with A. Need to get another seat for when he outgrows his current one, which will probably be around 4.5 years old. I think rear facing is important if you want your child to be as safe as possible, all the research I did was compelling enough to make me buy him a rear-facing seat before all the regulations came into play. I’m sure you’ll all love the new seat! 🙂 x

    • Thanks Jenny i was really surprised when I read the research about what a huge difference it makes. If I knew then what I do now my oldest would have been rear facing too.

  3. The car seat laws here in the U.S. confuse me as well. My kids are 5,4 and 3 and all tall for their ages. But also all skinny. Great info and how cool that you got one of the seats to review! Thanks for linking up with #momsterslink.

  4. So much has changed since mine were babies, I think I’d be lost if we were ever crazy enough to have a third child! Well done for raising awareness lovely, and thanks for linking up to #PicknMix

    Stevie xx

  5. Thanks for this. Very good read.
    We bought the 2 way pearl today as DD 10 months is getting close to outgrowing her newborn maxi cosi pebble plus.

    I have 2 questions.
    1. Why do you say that it is safer to keep DD in the new born car seat for as long as possible
    2. Will she have outgrown the pebble plus when she reaches its maximum height of 75 cm even though she is much below the weight limit. She weighs 9.8kg.

    Thanks a lot

    • Hi Elizabeth – the advice from keeping newborns in the 1st carseat as long as possible came from Maxi Cosi – who sent me some information for this piece. That many people move their children out of this car seat too early.


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