Canine gestation is on average 63 days, or 9 weeks, but can be between 58-70 days. Like humans there are 3 trimesters; weeks 1-3, 3-6, and 6-9.
When a female is receptive to a male it's called a standing heat. When the male mounts and ties they can be "stuck" together for up to an hour. Do not force them apart or toss water on them, let them separate naturally to avoid injury.
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During pregnancy progesterone is increased, once a pregnancy if over and the bitch enters anestrus progesterone decreases. (https://www.animal-reproduction.org/article/5b5a606ef7783717068b4766)