Both pampers & huggies it's happened with. We are using huggies little snugglers & have been for awhile now. We just upped to size 3 a few days ago which fit awesome & size 2 was too small/tight. For the first time last night though when we got her for her midnight feeds, both times the pee had went out the back of her diaper making her back wet. The diaper stayed pretty dry. Also, when laying flat on our bed, same thing happens. It's like whenever she's at any type of angle, the pee leaks out. Our bed is flat so not sure why that happens. Her bassinet pad is super flat but she's been playing with her feet, lifting her legs & playing with the sides, so I'm guessing that's what did it. I'm a perfectionist so her diaper is on perfectly every single time. Liner & ruffles out, perfectly strapped on her etc. We have no problem with the diapers during the day. Only when she's lying down. We had to change her jammies twice cause of it. Anyone know why this happens? Never had this problem with my boy. Is there a different diaper for slim babies that may have better absorption with angles?