In my view, a gynaecologist should know better, and here's why. They can deliver a baby and tell straightaway that the baby has Down's Syndrome, because of the appearance of their face, but a gynaecologist cannot look at a newborn baby and say, "That baby has autism." It's not something that comes up until later.
People may think that they're paying you a compliment, but in my view, it's almost like if someone with blonde hair and blue eyes and light tan skin tells you their grandmother was half-Chinese and half-Australian Aboriginal that they're lying. You shouldn't expect them to go and extract their family tree and say, "Okay, here's my parents' marriage certificate, Groom's Name: Graham Lucas, Bride's Name: Michelle O'Reilly. Here's my maternal grandparents' marriage certificate, Groom's name: Thomas O'Reilly, Bride's name: Polly Choo. Here's my mother's birth certificate and the names match. Here's my maternal grandmother's birth certificate: Father's Name: Wing Lee Choo, Mother's Name: Mary Noonuccal."
You should believe somebody if they tell you they're autistic.