Posted 4/5/2017 10:37 PM (GMT -5)
From the last data I saw, if one parent has IBD, the chances of each offspring getting IBD are around 10%.
If both parents have IBD, the chances for the children are probably higher - but if I recall correctly, there isn't enough data (ie, there hadn't been enough parents where both have IBD to get good numbers), so just how much higher the odds are is kind of fuzzy.