If you would like to carry your baby forward facing in a sling or carrier then you need to be aware of their airway. When babies carried parent-facing they naturally rest their head against their parent's body. This helps maintain an open airway in young babies who cannot maintain their own airway. When babies are forward facing in a sling or carrier they cannot rest their head, so they must be able to maintain their own airway for the position to be safe. It is for this reason that manufacturers only recommend facing outwards in a carrier once a baby has excellent head control . Usually not before 4 months.

For the same reason it is not recommended to let a child of any age fall asleep in this position, as when they fall asleep they relax and their head flops forward, which can compromise their airways. your baby sleep in that position.