From birth
Do not use the included Toddler Seat alone before 3 months. For a newborn, use one of UPPAbaby’s approved from-birth options: Bassinet V3, Infant SnugSeat with the Toddler Seat fully reclined, or a UPPAbaby Aria™/Mesa® infant car seat. The Bassinet, Aria™, and Mesa® attach directly without adapters.
From 3 months
The included Toddler Seat is approved starting at 3 months, up to 50 lbs and 40 in. Before 3 months, continue using an approved from-birth setup.
When the child begins to sit upright in the seat
If using the Infant SnugSeat, remove the wedge insert at this point. The product page also says the SnugSeat can transition into a plush comfort liner as baby grows.
When the infant begins to push up on hands and knees or reaches 20 lbs., whichever comes first
Discontinue Bassinet V3 use and move to another approved Vista configuration.