Make custom events exported in Geni GEDCOM files

When I export GEDCOMs from Geni and then import into other tree programs, Geni-made custom events seem to be totally lost.  For example, I often add "Immigated from ..." events to a Geni profile.  But when I look for such events after GEDCOM import into MyHeritage or Legacy or Family Tree Maker, these events seem to vanish.