I do not know the answer for this question. I read a statement somewhere that 'a mothers milk is heavier when she gives birth to a male baby compared to when she gives birth to a female baby'. Is there any truth in this statement ?
I don't know, but I wouldn't mind ...oops, not going there.
Interesting question. Although I can't imagine why you would want to know, unless you just had a baby boy, (Congratulations!), and want to know if you should buy heavy duty milk bottles!
I found this at an Australian Health site, regarding losing weight after childbirth, no real answer to your question, sorry:
Breastfeeding mothers Breastfeeding mothers need about 3,000 more kilojoules each day, including about 30 per cent more protein. The amounts of some vitamins and minerals also need to be increased to meet the needs of the baby and mother. The nutrients of particular concern during breastfeeding are: Calcium Folate Zinc Magnesium Vitamin A Vitamin B6. If the mother's diet is continuously low in vitamins, her breast milk concentrations will also be low. Recommendations include: Eat foods that are nutrient dense - especially in calcium, which is typically leached from the woman's body to make breast milk. Eat and drink regularly - breastfeeding burns through extra kilojoules and may increase the risk of dehydration and cause constipation.