Horsetail and Calc Tea

I'm about to make my own Calcium Tea and am searching for Horsetail to use, but everything I read says not to use this herb during nursing or pregnancy, when the Dr. Christopher material says to definitely use it during just such times. So I guess I'm just looking for reassurance before using it (I'm breastfeeding), (and my baby is teething). I know our family has Calcium issues (varicose veins, crooked teeth, cavities (2, unfilled), etc.
Any thoughts?
Thanks! Angora Tweet