I have a friend who got her Breast Augmentation done about 9 years ago.  She went from a small B to a full C.  She was 26 when she got the Breast Augmentation.  Her height is 5′4 and she weighed 115lbs at the time. 
 
She is now 35 and just had her first child. Before getting pregnant she weighed 120lbs.  During the pregnancy her breasts got very large (full D) but she also gained 60 lbs during the pregnancy which brought her weight to 180.   
 
She is now about 5 months into breast feeding and is starting to ween the baby off of the breast feeding and onto the formula.  She has not had any problems at all with the breast feeding.  Her only complaint is it being slightly uncomfortable which her doctor said is normal for anyone with or without having a breast augmentation.   
 
Her breasts are still larger than before she got pregnant but are starting to go back to their normal size.  Her weight is now 140 and she said there has been no sagging so far.  She is still extremely happy she had the Breast Augmentation surgery done.