The tummy is in the midst of a comeback for Spring 2012, but these fashions have less in common with the tanned-and-toned Britney Spears–type midsection than they do with a demure 1950s-era bikini. If you’re more ab flab than ab fab, you’ll be relieved to see that the navel remains under wraps, with most designers choosing to highlight the upper abs instead. In on the trend are lines like Dolce & Gabbana, with a tropical-inspired bustier top and pencil skirt, and Emilio Pucci, pairing its belly top with a white ballroom skirt. Helmut Lang, Miu Miu, Nina Ricci, Prada, Roberto Cavalli and Proenza Schueler sent naked tummies down the runway, too. The collarbone and shoulders are also seeing the light of day, as off-the-shoulder looks prevail across labels. But proving that squishy abs aren’t always a high-fashion deal breaker, five-months-pregnant supermodel Alessandra Ambrosio walked the Colcci runway at São Paulo Fashion Week this past January. We doubt, however, that Alessandra’s abs were looking much worse for the wear under the drapey sweater she sported. Alas, experts say that no matter how vigorously and regularly a woman works out, she will only begin to see abdominal definition once she’s reduced her body fat to 14 to 15 percent of her total weight. Trainer to the stars Ary Nuñez, who works primarily with skin-baring singer Rihanna, says the key is to focus on the core muscles and do a ton of repetitions. Does that mean that, once again, it’s crunch time?