Large dogs should be given one full tsp. But I'm not sure that this will have the effect that you are expecting.
Instead, I would look into Homeopet (www.homeopet.com) and try their anxiety formula. We have had a LOT of success with this. It can be purchased at most petsmart stores.
Let me know if you still have questions!
Sorry! You were asking about Valerian compound. The dosage for your dog's weight is one full tsp.
Valerian does come in a pet formula and has been used successfully in dogs. The other ones have not.
How long will you be traveling? If it's only a few days or a short vacation, you really might want to think of getting a petsitter instead of trying to take her with you. A transatlantic flight does subject her (and all the occupants) to a level of radiation that may or may not be suitable for pregnancy.
I would be very cautious about using any kind of sedative, natural or otherwise, with a pregnant dog. We would typically advise acepromazine but that is not safe in pregnant or lactating bitches. And the homeopathic remedies cannot be considered safe because none of them have been formally tested by the FDA. Benadryl MIGHT be ok late in her pregnant, but definitely not during the first few weeks.
Does this help more?