Want to know how to keep breasts looking young? A new study of twins provides revealing information for patients on which factors help breasts maintain their youthful qualities as well as those that seem to diminish them.

Breastfeeding, daily moisturizing, and hormone replacement therapy may help breasts stay younger looking. By contrast, smoking, drinking alcohol, multiple pregnancies, higher body mass index, and larger bra and cup sizes contribute to accelerated breast aging, according to a new study in the September issue of the Aesthetic Surgery Journal.

“Identical twin studies like this one are very valuable because they allow us to control for genetic influences,” says lead researcher Hooman T. Soltanian, MD, of University Hospitals Case Medical Center and Case Western Reserve University School of Medicine in Cleveland, Ohio, in a new release. “This allows us to more accurately assess the impact of external factors on breast aesthetics, such as environmental and lifestyle factors.”

For the study, researchers recruited 161 pairs of identical female twins with a mean age of 47.6 years in 2009 and 2010. Aesthetic breast features were rated by plastic surgery residents using standard medical photographs. The ratings were analyzed against data on participants’ medical and personal histories to determine the significance of different external factors on breast appearance. Twins who moisturized their breasts daily had significantly fewer wrinkles in that area, and those who received hormone replacement therapy after menopause had a more attractive breast shape, size, projection, areolar shape, and areolar size. Women who breastfed had less attractive areolar size and shape, but better skin quality.

“ This study is significant because it clearly shows women what they can do right now to help slow the aging process and keep their breasts looking attractive, even without surgical intervention,” says Foad Nahai, MD, the editor-in-chief of Aesthetic Surgery Journal, in a news release.