This is an excellent article, with very wise advice on baby's weight loss within a the first couple of weeks of life. If you have concerns or questions about your newborn's weight loss and milk intake, you are of course advised to seek support from a Lactation Consultant (IBCLC), a Certified Breastfeeding Counselor (CBC), or a Certified Lactation Counselor (CLC). Any of these lactation professionals should be able to support you or point you in the right direction.
An excerpt is below and the full article can be read here.
"This weight loss has nothing whatsoever to do with breastfeeding and milk intake. In fact, the authors suggest that if clinicians want to use weight loss as a gauge of milk intake, they calculate baby’s weight loss not from birth weight, but from their weight at 24 hours. According to their findings, this could neutralize the effect of the mother’s IV fluids on newborn weight loss.
This is one more reason weight loss alone should not be used to determine when newborns need formula supplements. The Academy of Breastfeeding Medicine put this well in one of its protocols: “Weight loss in the range of 8-10% may be within normal limits….If all else is going well and the physical exam is normal, it is an indication for careful assessment and possible breastfeeding assistance.”