Remember mice are very prone to stress, they know what to do so leave them for now and tomorrow you can check the babies.\, have a head count and check for milk band if that makes you feel better.
In general mice are a lot less trouble and in close to 9 years of breeding I have never loss a mouse while giving birth which is not the case with rats.
Thank you I'll be sure to check in tomorrow. Will it be safe to move the mothers to perform a head count? I don't want to upset anyone