.field--name-field-media-oembed-video > .field__item{
    position: relative;
    overflow: hidden;
    width: 100%;
    padding-top: 56.25%;
    margin: 0 auto 1.5rem;
}

.field--name-field-media-oembed-video > .field__item > iframe{
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
    width: 100%;
    height: 100%;
    border: 0;
}