Like many middleagers, Rusty and Judy Glide long ago let their marriage settle into a hazy, too-comfortable state of coexistence. He spends his evenings alone in the garage; she silently drinks schnapps in the kitchen. But neohippie daughter Gretchen shocks them back to life when she declares that her forthcoming child will be raised in a ''gender-neutral'' environment replete with foam blobs and black onesies. (The movement's leader, Hael Vanhorn, is a ''cape wearer'' who ''inverted her name to add sexual complexity.'') Darlington treats the fusty Glides with sharp, batty glee while carefully avoiding self-parody. Yet for all of Maybe Baby's rich characterization and zippy plotting, she hurries through the final chapters, leaving the story to languish when it should pack its strongest, silliest punch. What's the rush, girl?