FORTY may be the new 30, but try telling that to your ovaries.

With long brown hair and come-hither curves, Melissa Foss looks — and feels — fabulous at 41. “I’ve spent hours of my life and a lot of money making sure I was healthy, and that my hair was shiny, my teeth were white and my complexion clear,” said Ms. Foss, a magazine editor in New York City.

So when it came to conceiving a child with her husband, a marketing executive, Ms. Foss wasn’t at all worried. After all, she noted, those same traits of youth and beauty “are all the hallmarks of fertility.”

Fifteen unsuccessful rounds of in vitro fertilization later, Ms. Foss now realizes that appearances can be deceiving. “I’d based a lot of my self-worth on looking young and fertile, and to have that not be the case was really depressing and shocking,” she said. The couple are now trying to have a baby with the help of a surrogate and a donor egg.

Advances in beauty products and dermatology, not to mention manic devotion to yoga, Pilates and other exercise obsessions, are making it possible for large numbers of women to look admirably younger than their years. But doctors fear that they are creating a widening disconnect between what women see in the mirror and what’s happening to their reproductive organs.