Beginner's guide to buying a car seat - from nine months

So, your baby is starting to look a little squashed in his first car seat. When's the right time to move him on to a bigger, forward-facing one?

The when-to-move-on question all boils down to weight category of the car seat you bought originally. If you opted for a Group 0+ category car seat (suitable for babies up to 13kg), you should be able to get at least two or three more months out of it. If you bought a Group 0 car seat (up to 10kg), though, things might be getting a little snug already and you'll be needing to get a new car seat pretty soon.

Safety
Don't be in any rush to change car seats if you don't need to: it's safest to keep your baby in her rearward-facing infant car seat as long as possible (and absolutely until he weighs 9kg and can sit up unaided).

When the time for change comes, though, you'll probably find you're faced with a choice of forward-facing car seats. It is arguably safer to put your older baby in a new rearward-facing seat – in Sweden, in fact, children are routinely kept in rearward-facing seats until they are four years old – but these can be hard to find in the UK (although at least one intrepid Mumsnetter has tracked down one to review). They also tend to be pricey and complicated to fit but you may feel it's worth spending the extra effort/money for what the Swedes at least believe to be top-notch safety.

Whichever direction you want your car seat to face, you need it it have an E Mark on it (confirming that the seat conforms to all the officially required safety standards) and you may also want to consider a car seat that has additional side-impact protection. It's really not wise to buy/accept a second-hand car seat, unless it has a E mark and its original fitting instructions and you're certain it's never been involved in an accident. Any previous accident (however small) could weaken the car seat's effectiveness should you then be involved in an accident yourself.

We do not ask members who review car seats to rate them for safety, as – thank goodness – most people do not get to test this particular feature first-hand. However, we would encourage members to check the latest safety reports and contact the manufacturer direct if they have any specific safety concerns.

Also as before, you'll need to be sure that the car seat you buy fits safely into your car. Many car-seat manufacturers do now provide a list of car models their seats will fit into but the only sure way to be certain is to try the seat out in your car yourself. Most retailers should let you try before you buy (if they won't, insist that they allow you to return the car seat if it turns out not to fit) and the best ones will actually help you put several in your car and advise you which ones fits best.

Weight categories
Remember that (supremely unhelpfully) child car-seats are categorised into groups by numbers and symbols, rather than by weight of the baby they should contain. So, this time round, you're looking for a Group 1 category seat, which is suitable for children from 9kg to 18kg and so should last your child until she is about four years old.

If your first car seat was a Group 0+/1 seat (a 'combination' seat, bridging the baby and small child categories), you can now smile smugly and simply turn the seat round from rearward-facing to forward-facing – assuming you can still find the instruction manual, of course.

If you're kicking yourself for not choosing a combination seat last time, you could splash out a little extra cash this time and get a Group 1/2/3 combination seat which can be converted, when your child's about four, to a booster seat that'll see her through to about the age of 11. If you're expecting (or planning) another baby, though, it may be cheaper just to buy a booster seat at four and pass the Group 1 seat on to a younger sibling.

Portability
This type of car seat doesn't come with a carry handle, so it's really meant for keeping in the car. If you're going to be shifting your seat between two cars, though, or using the seat regularly in other people's cars (remember to check it fits safely), do make a point of looking for one that is both lightweight and easy to install.

Ease of installation
You may remember that sinking feeling you had when you opened the instructions manual of your first car seat. The bad news is the second is likely to be just as tricky. The good news is that you probably won't be taking this in and out of the car nearly as often as you did the first seat. It is definitely still worth, though, checking out the ease of installation ratings in our Car Seat reviews.

As well as how easy (or not) it is to strap your car seat in the car, look at how fiddly it is to strap your baby into the seat. As he gets older and stronger (and potentially tantrum-prone at the prospect of car travel), the last thing you want is to a wrestling match to get him in.

Comfort
For long journeys, seats with head rests are essential to prevent your baby's head from lolling about or falling forward. And, if your regular car runs tend to coincide with nap times, you might find a seat with a 'recline' button rather handy. Some car seats sit higher up than others, which is great for your child to get a good view out of the window and can help prevent car sickness. Again, it's important to test the seat in your car before you purchase – some models were found to be too high for certain cars.

Car seats and the law
According to the car-seat law regulations that came into force in 2006, it is the driver's responsibility to check that children travelling in her car are "correctly restrained". You should know, then, that:

It is illegal to travel with a child under three in your car, unless the child is strapped into car seat that is suitable for her size. The only exception to this rule is travel by taxi or licensed hire car where there is no appropriate child restraint available (and, in which case, the child must travel in the rear of the car).
It is illegal to place the car seat of a child under three on a front passenger seat where there is an active frontal air bag fitted. (If you can de-activate the frontal air bag – and have done so – then that's fine.)
It is illegal for a child over three and under 12 (or 1.35m tall) to travel in the front or back of a car, unless the child is strapped into car seat that is suitable for her size. The only exceptions to this rule are: travel by taxi or licensed hire car where there is no appropriate child restraint available (in which case, the child must wear the adult seat belt); a short, unexpected but important journey where there is no appropriate child restraint available (in which case, the child must wear the adult seat belt); the presence of two other occupied child car seats on the rear passenger seat that prevent fitment of a third seat (in which case, the child must wear the adult seat belt); and travel in a car with no adult seat belts fitted (in which case, the child should travel unrestrained in the rear).

In other words, the legal regulations are slightly different for children over the age of three and children over three (find them here) but all children must still travel in an appropriate car seat until either their 12th birthday or they are 1.35m tall.