My daughter hasn’t spoken in five years. She never had many words, but they all disappeared just before she turned two. She used to clap her hands along to music, respond to her name and once tried to feed her baby doll Cheerios. Those skills …

I did not know that anything was unusual until I was seven months pregnant. Inside the exam room, the technician dimmed the lights and stood astride her mysterious station. She worked her probe into the hard rind of my belly and offered selections …

With diagnoses at a record high, some experts have begun to question our assumptions about the condition — and how to treat it.