He's seen them for the holidays for the last ten years. OPs mother died, meaning not only hasn't she spent a single holiday with her family in TEN years, she also didn't get to spend her mother's last Christmas with her. Plus she's 8 months pregnant. She will grieving her mother (and very likely the lost time with her mother at family at key events, like her first child and Christmas - future ones & every year for the last ten years.) She will be incredibly hormonal, probably very physically uncomfortable too. She will likely be very emotional.

Her husband doesn't want offer his unwavering support for her during any that, for just this one year out of the last eleven? Then yes, he IS an ass.