Accessing textContent within connectedCallback() for a custom HTMLElement

Within the connectedCallback() method of my custom element the textContent is returned as an empty string.

Essentially my code boils down to the following...

class MyComponent extends HTMLElement{
    constructor() {
        super()

        console.log(this.textContent) // not available here, but understandable
    }           

    connectedCallback() {
        super.connectedCallback() // makes no difference if present or not

        console.log(this.textContent) // not available here either, but why?!
    }
}

customElements.define('my-component', MyComponent);     

And the HTML...

<my-component>This is the content I need to access</my-component>

From reading about connectedCallback() it sounds like it's called once the element has been added to the DOM so I would expect that the textContent property should be valid.

I'm using Chrome 63 if it helps...