They have been know to eat still borns, live young and slugs. I do not think the live happens often though.
One babie is rare, were there any slugs in the mix? You may also start finding them roaming around if they could get out. The look of your female should tell if she is done giving birth and typically they don't stop until they are done. If she retains babies it can lead to some problems, most of which are not life threatning but can keep her from being a future breeder.
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Steve Perry
North Idaho.