(someone) has a gut feeling that (clause)

When English speakers talk about a "gut feeling" or "gut instinct", they mean a feeling about something that can't be logically explained. In the example above, the expecting mother doesn't actually know whether her baby is a boy or a girl. She's just guessing based on a feeling or suspicion that she has.

The "gut" is actually your stomach; English speakers think of the stomach as a place where feelings come from. When you worry about something, for example, you may get a nervous feeling in your stomach. The gut is also considered to be a place of wisdom. People often tell each other to "follow your gut".

The expression "a gut feeling" uses the verb "have":

I can't explain why I did it; I just had a gut feeling about it.

You can describe the exact feeling that you have with a clause like this:

I don't know about this deal; I have a gut feeling that I'm going to regret it.

The phrase "gut instinct" is similar to "gut feeling", but it's usually used in a slightly different form:

My gut instinct tells me that it's going to be a boy.

My gut instinct is that it's a boy.

It's a boy / It's a girl

When you're talking about the gender of a baby (whether it's a boy or a girl), you have to start by calling the baby "it". That's because saying "He's a boy" or "She's a girl" sounds silly and repetitive. So people say things like:

Is it a girl?

We didn't know if it was going to be a boy or a girl.