In an ideal world full of all high functioning people, this might be true. In the world we actually live in, I have personal experience that says it isn't true. In the case I'm thinking of, the woman didn't want to admit to herself that she was pregnant and didn't admit it to herself until the 7th month. She tried to abort the baby, but she couldn't find a doctor who would abort a healthy fetus that posed no risk to the mother.

That said, I think it's a fair screening question. In fact, I'm not sure I could think of any screening question that wouldn't be fair. You're trying to find a match that's good for you. You have a right to ask about anything that matters to you.