Ling Yang or Antelope's Horn is very cooling isn't it? I remember a colleague recommending that I should drink some after a bout of viral fever. Like everything else, i reckon that it is best to take it in moderation especially when breastfeeding or pregnancy is involved. When you are at the medical hall purchasing these herbs, always check with the experts if it is suitable for you and baby.
It is safe to drink when breastfeeding in a moderate amount. Not to drink too much or drink a long period of time. I have taken it once when I was sick and baby is fine.
This link might help:http://pregnant.sg/articles/restore-balance-childbirth-using-tcm/