Without knowing precisely which herbs you are taking, I cannot answer for sure (and, even if I did, there's no guarantee...), but here's my opinion.
Chances are that the manufacturer is covering its bases, legally. You are probably safe using the herbs, as long as herbs are all you are using. There are some herbs which can cause problems, however, so you should probably look up the herbs listed on the label to see what effects, if any, are known.
For example, the herb Feverfew is used to induce bleeding after birth, to help clean up the uterus. When my wife took it many years ago (while on the pill -- someone recommended it to her for "headaches"), it caused her to appear to be menstruating. This is definitely not an herb you want to be taking if you want to try to conceive, as it could easily cause the zygote to be expelled just as it's attempting to establish itself in the uterus.
This is merely an example of an herb which could cause problems with conception. It is not an example of an herb which is commonly found in parasite cleanse formulas.
Even so, why not finish your parasite cleanse and give your child a much cleaner environment to develop in, rather than conceiving now while parasites are still a concern?