As a babywearer, i sometimes forget there are people that have reservations about carriers, to me babywearing is a no-brainer, it simplifies my life and brings me joy. I all to often forget my reservations when i first tried a wide base carrier with my second son.
I had only ever used a Wilkinet and Stretch Wrap, so when i purchased my first Mei Tai i will admit i was worried how my son could possibly fit into the wide seat of the carrier.
First thing is first, age plays a huge role in how wide a child will be able to spread their legs. New babies won’t be able to and there is risk of over-extending their leg gap too early if forced. So as a rule of thumb its advisable to wait until your child is starting to lift up their legs towards their chest and roll in a controlled manner. This signifies the developmental stage where the child is naturally opening this area up and often occurs around 3 months of age.
Babies will tell you if they are uncomfortable by crying and squirming, however do not assume that the carrier is too wide straight away as there can be many other reasons they are crying. If you can hold baby the same way in-arms then the chances will be they are upset for another reason.
The act of separating the hips is know as abduction and evidence shows that the most optimum angle for abduction is 90° (45° each leg from the mid-line). This can be a concern for larger ladies or for carriers that are wider than standard, for example toddler carriers. Using a carrier such as a toddler carrier before the child is the correct size for it, whilst has no proven long term issues, i feel it’s best to err on the side of caution and avoid or cinch in the waist to reduce the width if possible. This can be done by using a piece of string, thin scarf or a specialised carrier waist cincher.
The angle of which the legs bend ( flexion) is also important and optimum is around 100-120°, however the wider the abduction of the leg the lesser the flexion should be. Or in simple terms the wider spread, the lesser the legs have to be bent. Which isn’t a great concern for most soft structured carriers as they tend to promote a more seated position (90° flexion) than a seated squat (120° flexion).
If you are in doubt or worried the best advise i can give is see your local sling library or consultant for further advice.