Breastfeeding won’t make a new mom’s breasts sag, but having more babies might, a new study indicates.

"A lot of times, if a woman comes in for a breast lift or a breast augmentation, she'll say 'I want to fix what breastfeeding did to my breasts,'" said University of Kentucky plastic surgeon Brian Rinker. So he decided to study any possible connection.

Rinker and his colleagues interviewed 132 women who came in for breast lifts or augmentation between 1998 and 2006. On average, the women were 39 years old, and 93 percent had experienced at least one pregnancy. Among the mothers, 58 percent had breastfed at least one of their children. The average duration of breastfeeding was nine months.

The researchers evaluated the womens' medical history, body mass index (BMI), pre-pregnancy bra cup size and smoking status.

The results of the study, presented this week at a conference of the American Society of Plastic Surgeons, showed no difference in the degree of breast ptosis (or sagging) between women who breastfed and those who didn't.

The main factors that did affect sagging were age, smoking status and the number of pregnancies a woman has had.

Rinker noted that the smoking connection made sense because "smoking breaks down a protein in the skin called elastin, which gives youthful skin its elastic appearance and supports the breast."

Pregnancy also "has a very strong contribution to breast ptosis (sagging)," Rinker said in an email interview. "In fact, our study showed that those negative effects increase with each pregnancy."

Rinker says this finding should alleviate the fears of new mothers over what nursing their child might do to their breasts in the long run and will encourage them to breastfeed because of the health benefits to their infant.

"Women may be reluctant to breastfeed because of this unfounded myth that doing so means the end of youthful breasts," Rinker said. "Now, expectant mothers can relax knowing breastfeeding does not sacrifice the appearance of their breasts."