I dug into my documentation and found a clipping from the French  IBFAN
Africa journal  . I had kept it because in France we have an important
moslem community . The article is on Ramadan, the fast every moslem has to
follow for a month every year. They are to abstain from drinking and eating
during the day. 
The author  pleads for a good information of moslem pregnant and
breastfeeding women that they are exempted from the fast (the problem is
that they will have to "catch up" on their own later).
Studies have shown that breastfeeding women who fast lose 7.6% of water in
their body and that their milk have a different concentration  in lactose,
sodium and potassium.This can end up in a drop in the lactation, babies
being put on cow's milk  with the consequences we know.
He does not give the references but there is an address you may want to
contact

Fondation Hassan II pour la recherche scientifique et médicale sur le
Ramadan
 ( Foundation for scientific and medical research on Ramadan), 
 19 rue Tariq Bnou Ziad
Faculté de Médecine et  de Pharmacie
Casablanca   Maroc
fax: 212 2 47 12 90

There are certainly information on this topic that can be gathered from
other religion where fasting is a regular prescription.

Gisele Laviolle LLLL; IBCLC from a Paris suburb , France

 Ps :  I fully support those who ask  everybody to put a specific country
and geographic location in their signature,
 thanks