Although beechnuts are edible and known to be rich in tanins, we do not have substantial information to suggest or conclude that they are safe to eat during pregnancy. Hence, it is recommended that you consult with your doctor before having beechnuts while you are expecting.
Taking common medicines during pregnancy, a summary of NHS UK guidelines
You should definitely check with your doctor before taking any medication during pregnancy. Even for medication you were already on at the time of getting pregnant, now needs to be approved by your doctors as