IT was the pale green and pink striped bikini that did it.

When Sandra Cornier, a mother of two from Brooklyn, looked at a recent photo of herself taken at Manhattan Beach, N.Y., she didn’t like what she saw. She had been nursing her son for 11 months, and now she could barely fill out the bathing suit top.

She made a decision: She would have breast implant surgery, and right away, because she wanted to be cozy in her favorite bikini by the end of the summer. She did not have the cash available, but she was willing to borrow.

“I just wanted to proportion myself out and look like I did before I had children, simple as that,” said Ms. Cornier, 33, who is married and works for a government agency. She took a loan for $10,800. “I did not want to wait two or three years to save up for surgery.”

Cosmetic medicine used to be the province of the rich and celebrated who would pay cash or write a check up front for their tummy tucks and eyelid lifts. (Such procedures are not typically covered by health insurance.) But in the last five years, with the advent of reality shows like “Extreme Makeover” and the popularization of nonsurgical treatments like lasers and wrinkle injections, people with blue- or pink-collar incomes and Beverly Hills ideals are embracing vanity medicine.