Get page height in embedded report?

We embed PowerBi reports with  "layoutType: models.LayoutType.Custom" and "displayOption: models.DisplayOption.FitToWidth". How can we retrieve (each) page height in order to adapt the iframe container height accordingly (and remove the vertical scrollbar) ?

(we cannot get directly iframe.innerContent height due to cross-domain policy)

(with DisplayOption.FitToPage,  we have oversized left and right margin in average).