GMC 2009 Sierra 1500 Crew Cab Owner's Manual page 48

CAUTION:
{
Never do this.
Never hold an infant or a child while riding in a
vehicle. Due to crash forces, an infant or a child
will become so heavy it is not possible to hold it
during a crash. For example, in a crash at only
40 km/h (25 mph), a 5.5 kg (12 lb) infant will
suddenly become a 110 kg (240 lb) force on a
person's arms. An infant should be secured in an
appropriate restraint.
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