Alan - Most dewormers are perfectly safe at all stages of gestation. I do know that Valbezen is not supposed to be used during a time period - like the first 45 days of gestation?? Too lazy to go down cellar to find product & read label - but there is a time period you can't use it. You would have to read the label of the product you use. I know a Safeguard rep that used to recommend drenching the cows as you put them thru the chute for breeding. Perfectly safe on them.
Other producers may know of other products that aren't safe, but Valbezen is the only one that I know of that does have a warning.
Edit - also, on the testosterone - there is a specific dosage & time schedule. Did it many, many years ago - you would have to check with a vet. Seems like we had to inject daily for about a week, than hit her maybe once a week. But, I really don't remember - just remember it was a long drawn out affair - but worked GREAT.