Rebecca,
You are right to question the article lumping the "conditions" of
breastfeeding and pregnancy with respect to the use of medicinal herbs.  The
FDA assigns one of five Pregnancy Risk Factor (PFR) categories to prescription
drugs which indicates the potential for causing birth defects.  The American
Academy of Pediatrics puts out a completely different list of drugs (soon to
be updated) that are considered compatible or not compatible with
breastfeeding.  Some drugs are contraindicated in pregnancy but considered
safe in breastfeeding and vice versa.  Generally, the potential risks to the
baby are far less during lactation:  the baby isn't as vulnerable in terms of
development and the placenta "filters" out much less than the breast does (but
there are exceptions).

As you suggest, herbs would also be potentially dangerous in pregnancy yet
safe in lactation (or vice versa).  An important difference is that herbs can
vary in concentration, and even in terms of active pharmacologic agents, from
batch to batch whereas prescription drugs are much more standardized.  The
maximum dosage of the active/potentially toxic ingredient(s) in herbs is
typically unknown, thus maximum nursling exposure is impossible to predict.

With drugs and herbs the variables of the nursing relationship are potentially
important:  age of child, timing of nursings, percentage of total diet from
breastmilk, etc..  Certainly the risks are different for  1 week old, 1 year
old, and 4 year old nurslings.  In pregnancy the risks are different in each
semester.  Lumping pregnancy and lactation together does little to clarify the
issues.  Warmly, David Ziska, Pharm.D., and Elaine Ziska, BS, lay bf counselor