
First and larger litters seem to be early, but my breed tend to be early anyway.
My own last litter were born 25th due on 28th and a friends bitch had hers on the 9th and were due the 12th, boith maidens with average size litters.
My earliest has been 5 days early, most are born before due date and have only ever ahd a few litters born due date or later, and these have been the result fo earleir matings than the usual day 15+ that mien seem to prefer.