The issue focused on a series of questions: "Can you imagine having a baby, and then you discover the child you're having isn't yours?"

"It's a really hard question to answer," said Ms. Hirschfeld, a psychologist at the University of California, Davis.

In this case, she said, it's unclear whether a doctor who has not performed the birth has actually given birth. And it is unclear whether that birth was in fact the child that was discovered to be hers