Body of fetch returning empty object in Next.js API endpoint call

I am having trouble with making an API call in Next.js that is deleting an item in a database. I am using the "body" field of the fetch to send a string to the API. The fetch call is being made in a Next.JS page and the API endpoint is in the API folder generated by Next.js. When I attempt the console.log the body from the request it is returning an empty object. Below will be the code for the page and then the code for the API endpoint. A screenshot of the console.log from the API endpoint will also be given.

Page

   const handleRemoveItem = useCallback(async(event) => {
        event.preventDefault()
        
        var itemSKU = event.target.value;

        const response = await fetch('/api/SB-RemoveProduct', {
            method:'POST',
            body: itemSKU
            }).then((r) => {
              return r
            }).catch((err) => {
              throw(err)
            });
        var deleteConfirm = await response.json();

        console.log(deleteConfirm);
    },[])

API endpoint

export default withSession(async (req, res) => {
    var itemSKU = req.body

    console.log("You are here 1");
    console.log(itemSKU);

    switch (req.method) {
        case 'POST': {
            var productRemoved = await removeProduct(itemSKU, req, res)
            return productRemoved;
            break
        }
        case 'GET': {
            console.log('try writting a route')
            break
        }
        case 'DELETE': {
            console.log('try writting a route')
            break
        }
        case 'UPDATE': {
            console.log('try writting a route')
            break
        }
    }

});

export const removeProduct = async (itemSKU, req, res) => {

    var params = {
        TableName: "products",
        Key: itemSKU
    }
    console.log("You are here 2");
    console.log(itemSKU); // this console.log and the one above both return {}
    DB.delete(params, function(err, data) {
        if (err) {
            console.error("Unable to delete item. Error JSON:", JSON.stringify(err, null, 2));
        } else {
            console.log("DeleteItem succeeded:", JSON.stringify(data, null, 2));
            res.status(200).send(data)
        }
    });
    
}

EDIT 1:

After receiving some feedback, I added headers with the 'Content-Type': 'text/plain', 'Accept': 'text/plain' and ended with the same result. I also verified that the variable that I am passing into the body is a string. Below will be page for the code updated.

    const handleRemoveItem = useCallback(async(event) => {
        event.preventDefault()
        
        var itemSKU = event.target.value;
        console.log(typeof(itemSKU));

        const response = await fetch('/api/SB-RemoveProduct', {
            method:'POST',
            body: itemSKU,
            mode: "cors",
            headers: {
                'Accept': 'text/plain',
                'Content-Type': 'text/plain'
              },
            }).then((r) => {
              return r
            }).catch((err) => {
              throw(err)
            });
        var deleteConfirm = await response.json();

        console.log(deleteConfirm);
    },[])

EDIT 2:

Following the suggestions from a solution below, I was able to return a different value for itemSKU than what I had before. This time, instead of the item being empty, it returned as undefined. The changes I made are below:

page:

const handleRemoveItem = useCallback(async(event) => {
        event.preventDefault()
        
        var itemSKU = event.target.value;
        console.log(typeof(itemSKU));

        const response = await fetch('/api/SB-RemoveProduct', {
            method:'POST',
            body: JSON.stringify({itemSKU}),
            }).then((r) => {
              return r
            }).catch((err) => {
              throw(err)
            });
        var deleteConfirm = await response.json();

        console.log(deleteConfirm);
    },[])

API Endpoint:

export default withSession(async (req, res) => {
    var itemSKU = req.body.itemSKU //req.body.itemSKU is returning undefined.

    console.log("You are here 1");
    console.log(itemSKU);

    switch (req.method) {
        case 'POST': {
            var productRemoved = await removeProduct(itemSKU, req, res)
            return productRemoved;
            break
        }
        case 'GET': {
            console.log('try writting a route')
            break
        }
        case 'DELETE': {
            console.log('try writting a route')
            break
        }
        case 'UPDATE': {
            console.log('try writting a route')
            break
        }
    }

});

export const removeProduct = async (itemSKU, req, res) => {

    var params = {
        TableName: "products",
        Key: itemSKU
    }
    console.log("You are here 2");
    console.log(itemSKU);
    // DB.delete(params, function(err, data) {
    //     if (err) {
    //         console.error("Unable to delete item. Error JSON:", JSON.stringify(err, null, 2));
    //     } else {
    //         console.log("DeleteItem succeeded:", JSON.stringify(data, null, 2));
    //         res.status(200).send(data)
    //     }
    // });
    
}