Early Pregnancy

There is never a “best” anything in Chinese Medicine for “x” condition - proper diagnosis is key (see “how to choose a formula” for more). For pregnancy related nausea I find acupuncture far superior to anything herbally, but if herbs were the only options a commonly used formula would be bao he wan.

As for si wu tang that is generally safe during pregnancy, but again, nearly any formula can be justified for the right diagnostic reasons - your reasoning for using is of utmost importance, not choosing it generally.