Thankfully, there are usually a series of signs that you have so you can know when labor will begin. I was able to relax for most of this week when I realized that one of my girls wasn't nearly as far along as I had thought she was. Yesterday morning, she finally gave me the first signs, and I told a couple of people that I knew we'd be expecting puppies in 24 hours. Sure enough, that part didn't fail.
A drastic drop in temperature has been my first sign (although some breeders don't see this in Havanese all the time), a refusal to eat, digging in bedding and trying to create a nest, and heavy panting all come to mind. Those are the four signs that let me know it is time to be ready. In addition, if you have done progesterone testing, you can tell the exact day of ovulation and dogs are pretty predictable for going into whelp at a certain date after that.
As of this morning, I have only whelped five Havanese litters. Every whelping has been different for me. There always seems to be one or two moments of huge stress and worry, and an amazing amount of relief to see some healthy, squirmy, twitchy puppies all nursing and snuggling with their mother.
Two different times, it was so incredibly stressful and a puppy was stuck long enough that I just knew the puppy was a goner and I was doing all I could to save the mother. Both times, I was wrong and the puppy was just fine. Piaget was one of them. He was such a big puppy and she had difficulty pushing him and I was tugging away at that body just sure I was going to injure her or harm him if he was alive. Both were fine for it.
I think I've had my emergency vet's number dialed for 3 out of 5 of the litters and then as the situation was being explained, I would yell, "We've got it - thanks!" and have to hang up. I think the emergency vet has been our magic trick a couple of times. (Not really, but you know what I mean.)
This morning's whelping was my hardest physically, but definitely my easiest overall. I stayed up last night knowing puppy arrival was eminent, and hard labor signs did start shortly after midnight, but the first puppy wasn't born until nearly 7am. By 8am, five puppies (one of which was a surprise) had been born by practically falling out with one push. Each one was still in the sac and ready for attention. I was running on adrenaline because that is barely enough time to clean, weigh and examine each pup before the next one was out. By noon today I was in dire need of a quick nap.
I don't even know if I answered what you were asking. It's just very fresh on my mind today.