@testing-library/react with msw/node; window.fetch not returning body on POST

I created a simple application using create-react-app. I am now trying to write some automated test cases using @testing-library and Mock Service Worker. For reasons unknown to me when I POST a request using Window.fetch (or just fetch) the body of the response is not returned.

I am using the following dependencies:

    "@testing-library/react": "^11.2.5",
    "@testing-library/user-event": "^12.7.1",
    "msw": "^0.28.0",
    "react": "^17.0.1"

I have the following test:

import { rest } from 'msw';
import { setupServer } from 'msw/node';

const MOCKED_URL = 'http://mock.example.net:8080/foo'
let server = setupServer(
    rest.post(MOCKED_URL, (req, res, ctx) => {
        return res(
            ctx.status(200),
            ctx.json(req.body),
        )
    }),
)

beforeAll(() => server.listen())
afterEach(() => server.resetHandlers())
afterAll(() => server.close())

test('send POST request with body via superagent', async () => {
    let response = await window.fetch(MOCKED_URL, {
      method: 'POST',
      mode: 'cors',
      cache: 'no-cache',
      headers: { 'Content-Type': 'application/json' },
      body: { bar: 6, baz: '34' }
    });

    console.log(response);
    expect(response.body).toMatchObject({
        bar: 6,
        baz: '34',
    })
});

The output from the console.log(response) is

        type: 'default',
        status: 200,
        ok: true,
        statusText: 'OK',
        headers: Headers {
          map: { 'x-powered-by': 'msw', 'content-type': 'application/json' }
        },
        url: '',
        bodyUsed: false,
        _bodyInit: Blob {},
        _bodyBlob: Blob {}
      }

Can anyone explain why the body is not returned and how I can get this test to work?