Pregnancy can take a toll on the shape of breasts, but breastfeeding doesn't make them wilt more, according to researchers.

The ligaments and skin that support breasts may stretch as a pregnant womanâ??s chest grows fuller and heavier, according to the Mayo Clinic. When her breasts shrink back down after she delivers her baby, the extended skin and ligaments may not return to their former shape, and neither may her breastswhether she has chosen to nurse or not.

Some factors do make matters worse.

In a 2007 study of 132 women, breastfeeding did not have a significant effect on breast ptosis, the medical term for sagging breasts. But age, smoking and the number of pregnancies a woman had did contribute to the shape of their breasts, according to University of Kentucky plastic surgeon and researcher Brian Rinker. The older a woman is and the more pregnancies she's had, the more her breasts are likely to shrink.

"Smoking breaks down a protein in the skin called elastin, which gives youthful skin its elastic appearance and supports the breast... so it would make sense that it would have an adverse effect on the breasts," Rinker said.

Being overweight may also lead to the same drooping effect.

Despite the deflating news that sagging breasts are somewhat inevitable for pregnant and aging women, mothers may find comfort knowing that nursing is not the culprit.

"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."

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