I too have worked with post-GBS mothers who have not been able to produce a full milk supply.  Lots of breast ptosis & glandular tissue not easily palpated.  Certainly, the causes are multifactorial (PCOS, cosmetic breast surgery, infertility issues, etc) and more research is needed.  I also have noticed a trend of post-GBS moms having SGA/IUGR babies...maybe placental issues?  Could lead to inadequate secretion of hormones needed for prenatal breast growth & differentiation...setting them up for failed lactation.
     Here is some great food for thought by J. Stefanski who wrote in Today’s Dietician, (2005):
      "The human body adapts to the changing demands of lactation by increasing nutrient intake, improving absorption,  decreasing excretion and using tissue stores.  But, for the woman who has undergone WLS, can her body overcome the physiological changes the surgery has created to adapt for lactation?"
     In addition, we know from recent research that overweight/obese women have delayed onset of lactation with a blunted prolactin response.  Well, J. Blankenship writes, what about the women who loses weight via weight-loss surgery...does her body act like an overweight one, even though she has lost the weight?   Lots of questions...& you are right, we need more studies.  Looking forward to seeing your phenomenological study this summer at ILCA.

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