Can I use a different mattress pad or add extra bedding?

No, you must use only the mattress pad provided by Graco with dimensions of 27" x 39" (68.5 cm x 99 cm). The playard mattress pad is specially designed to prevent suffocation with a solid base, specific length and width, and less than one inch thickness. Using a thicker or different sized mattress pad may allow a child's head to get trapped between the mattress pad and the playard side, causing suffocation.