レスポンシブなYouTubeの埋め込み

html

<div class="iframeWrap">
<iframe width="560" height="315" src="https://www.youtube.com/embed/_iTJ4WHDhu4?rel=0" frameborder="0" allowfullscreen></iframe>
</div>

scss

.iframeWrap {
    position: relative;
    width: 100%;
    padding-top: 56.25%;
    iframe {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
    }
}