How can I display backend API error messages using fetch in Next.js?

I'm working on a Next.js sign-up/login form and I'm trying to display error messages sent from my Express backend. My form submission function calls an API using fetch, and although I see the message in the network tab, the console log of the response doesn't show the message itself.

I call this function on form submission:

JAVASCRIPTCopied
const formSubmit = async (e, name) => {
    e.preventDefault();
    const url = `${url_prefix}/${formName}`

    try {
        const response = await fetch(url, {
          method: "POST",
          headers: { "Content-Type": "application/json" },
          body: JSON.stringify({ user }),
        });
        console.log(response) // show message here
        if (response.ok) {
            router.push('/validateuser')
        } else if (response.status === 401) {
            msgFn({message: 'Invalid Credentials', type: 'F'})
            setTimeout(() => {
                msgFn({type: ''})
            }, 3000);
        }
      } catch (error) {
      }
};

My Express backend has something like this:

JAVASCRIPTCopied
const createuser = async (req, res) => {
    try {
        console.log(req.body)
        const { username, email, password } = req.body.user;
        const userExist = await User.findOne({ email: email })

        if (userExist) {
            return res.status(401).send({message: 'User already exists.'})
        }
        const user = await User.create({ username, email, password })

        const new_user = await User.findOne({ email: email })
        const userId = new_user._id

        await LoggedUser.deleteMany({});
        const loggedUser = await LoggedUser.create({ username, email, userId })
        res.json({ message: 'User Created' })

    } catch (error) {
        console.error(error)
    }
}

If the user email already exists, I send back 'User already exists' from the backend (visible in the network tab), but I can't access this message in my response object when logging it. I want to properly extract and show the message from the backend, rather than relying on checking HTTP status codes. Any advice on how to do this?