Here are my rules for knowing when your female dog (bitch) needs help with the delivery of her puppies. These are general rules that apply to all breeds. Please consult your veterinarian for additional breed-specific guidelines. Also, get a pre-whelping x-ray. It will tell you how many puppies to expect and if any are too large for a vaginal delivery.
1) The bitch has been pregnant for over 72 days from the breeding date.
2) More than 24 hours have passed since her temperature drop without any signs of labor.
3) The female has been in stage one labor for 8 hours or longer without progressing to stage two.
4) Twenty minutes of active, hard labor without a puppy born.
5) A dark greenish to brown vaginal discharge (lochia) without a puppy born within fifteen minutes. (Some veterinarians use one hour as the cut-off instead of fifteen minutes. I use a shorter time frame to allow you to get help before the puppy dies.)
6) Four hours between puppy births with no straining.
7) Puppy stuck in the pelvic canal.
8) If you feel something is wrong, never hesitate to get help! Your veterinarian can check the fetal heart rates for distress with an ultrasound and take action if needed. As a veterinarian, I would much rather check and make sure everything is progressing normally, than wait and lose a puppy.
For a description of the stages of labor see the blog post “Normal Stages Of Whelping In Dogs”.
Source: Freshman, Joni. “Canine Dystocia Management”, Western Veterinary Conference Proceedings 2002.