
The only safe wormer to use on gestating bitches is Panacur 10% from day 40 til 2 days post whelp. Any other wormers should have been given at the usual times and a week before mating (well thats how I do it).
Ask your vet about what the main concerns are with regard to using other wormers during pregnancy, especially in the first few weeks. It should have been stated in the instructions about suitability(or otherwise) for pregnant bitches.
Back to the original question, its probably just the equivilent to our morning sickness. Nothing to be concerned about.