
Under the circumstances (tummy bug) I'd leave it now - we wormed before our bitches came into season, based on their normal cycle. And then wormed again when we gave the puppies their first worming - at 2 weeks. I have never wormed during pregnancy. And only with my first 'litter' (solo puppy) did I see worms after being wormed - masses of 'em. I hadn't pre-wormed mum so I learnt my lesson there (novice breeder at the time!).
My puppies were wormed from 2 weeks, and then every two weeks to the time they went home, with a full history of what worming had been done, when and what with (Sherleys syrup). And with the advice the puppy was wormed again by around 3 months - depending then, on their vet's advice. And again, apart from the first solo puppy, I never saw any worms from our puppies.