It is always assumed that breast feeding causes droopiness of the breast, or breast ptosis. However the evidence is that it is not a major factor.It is true that the risk of ptosis increases with each pregnancy. However other factors are more important. For example age, being overweight, increased number of pregnancies, smoking , and larger pre-pregnancy breast size, are all much more important than breastfeeding in creating postpartum breast droopiness.
This is good news for mothers who want to breast-feed, because it is not likely to increase ptosis.