A great question because women often ask this when they are considering breast augmentation.  Most breast augmentations are done in women who have not had a pregnancy.  The women who have breast implants are usually very glad that they have them after their pregnancies since there is a tendency to lose breast volume after a pregnancy and after breast feeding.  Your breasts after a breast augmentation should continue to look good as long as you do not gain more than about 25 to 30 pounds during your pregnancy.  Any more weight gain than that carries with it the possibility of stretching the skin of the breast out and compromising the result.
Breast feeding after pregnancy should not be an issue as we normally do not cut any of the ducts and in fact rarely even see your breast tissue during a breast augmentation since breast implants are placed completely below the breast itself.
As you do your research make sure you consider a 24 hour rapid recovery breast augmentation with no narcotics using the natural feeling, gummy bear breast implants from Sientra.  Sientra’s shaped implants will give you a great natural look and they have absolutely the best warranty on the market with the lowest complication rate.