Pill period

Magdalena

Hey guys just a quick question. I'm on the combined pill (microgynon), and was wondering if the period you get in your break is still an indication of whether or not you may be pregnant? I remember reading somewhere that you bleed due to the withdrawal of oestrogen (? or a different hormone) and that you would not bleed if pregnant because you wouldn't have an oestrogen withdrawal. Am I correct in thinking this?