Is it common for a mouse to abort her first litter?

My mouse just started to look 'pear' shaped, and I figured she'd be giving birth soon. So when I saw some blood in her box, I thought she had, but she was curled up in a corner alone, with tiny babies dead and stuck to the paper towels that she had used to line her nest. I haven't introduced any new males, and her two cage-mates were leaving her alone. Just wondering if it's common for a mouse to abort her first litter.