There’s nothing quite like a beaming expectant mother strutting her belly down the runway to put a smile on your face. (In fact, the front row at Liz Lange’s maternity show could have been an advertisement for Crest Whitestrips.) But ladies-plus-one deserve a moment in the spotlight and clothes that aren’t frumpy. After all, they’re battling hormones, bizarre food cravings — hence the impressive array of doughnuts backstage — and weight-gain insecurities. Lange, who realizes that maternitywear shouldn’t just be about extra-stretchy fabric in the tummy area, delivered a collection of fun, casual looks that picked up on preppy. She created great tennis sweaters and generously sprinkled kelly green, navy blue and red throughout. Printed baby-doll dresses were charming, and bright satin kept things sexy for evening.