Gross, but true. You'll need at least two large boxes of the most absorbent sanitary napkins you can find—ideally ones designed specifically for postpartum bleeding or overnight use. You'll get some in the hospital, but they usually don't have the panty-saving wings. Tampons are taboo during the postpartum period, so don't even consider using any you might have kicking around in the back of your bathroom vanity.
Always Maxi Pads Overnight With Wings
$6.99 for 28 at Drugstore.com