Echinacea is a great herbal/natural remedy for colds and flu and is a good cleanse for the body. But I did find this:
Echinacea isn't recommended during pregnancy because it could stimulate your uterus and cause premature labor. And since your immune system changes when you're pregnant to give you extra protection against illness, you don't want to take anything that could interfere with that process.
The one published study on echinacea in pregnancy didn't find any increased risk for birth defects, but it was too limited to be definitive.