When James Goodrich separated the head-joined twins Carl and Clarence Aguirre a year ago, he performed a singular medical feat. He also entered a world of squabbling over just what, exactly, he accomplished.

Many of the city’s mothers-to-be are counting every carb and pushing their heart-rate monitors to the limit to stay skinny and sexy while pregnant. Is this harmless vanity? Or a New York obsession gone too far?