I feel like i have a very good Dr, and when i asked her about it she said basically that yes, it sometimes can reduce supply, but she said that women who are not currently having any problems usually do not. She said that the ones that seem to have problems while on the pill with supply, are the ones that are having supply problems/a tough time anyway.
She also said that if it seemed like i had supply issues after starting it, that i could just stop and those issues would go away.
FWIW i did take them for a few months while BF. Had no supply issues, but i had even worse lack of libido while on them. BF for me kills it regardless, its just even worse (if thats possible) while on them so i stopped.
SAHM to 4 cats, DS 5/09, DD 3/12 and 3# due 4/15. Home birthing, non vax, anti circ, co-sleeping, breastfeeding, real food eating pretty darn crunchy mama.