The RTÉ star and her husband Padraig McLoughlin welcomed their second daughter last month.
Taking to her Instagram Stories on Sunday, the 42-year-old urged her followers to donate to the Late Late Toy Show appeal after spending three nights in Crumlin with Grace.
She explained: “There is still time to donate to the Late Late Toy Show Appeal. We are only catching up now as we just spend three days in Crumlin with little Grace.
“Her breathing got very laboured on Wednesday so I brought her straight to A&E. She was diagnosed with bronchiolitis but thanks to the incredible nurses and doctors she’s home now and doing great.
“Hospitals are difficult places to be but a children’s hospital is on another level. But the care and compassion we received from the nurses day and night was unbelievable. I cannot thank them enough.”
“We got to go home this weekend but so many other families and their little mites didn’t. Please if doing any last minute shopping online, please donate if you can.”
Kathryn shared the first photos of baby Grace earlier this week after giving birth in October.
“1 month old already little Grace where has the time has gone,” she wrote on Instagram.
“She has filled our house and our hearts with a love I can’t even describe.
"The little mite has been quite sick the last week but thankfully looks like she’s on the mend.
“And in the midst of all the worry, late night cluster feeds, breast pumps, leaky boobs, giant knickers, cold coffees, heightened emotions and everything else that comes post baby, I wonder if life will ever return to something resembling normal??
“All I know is that the ferocious love and protection you feel for your little ones overrides physical exhaustion every time.
“Honestly, when I was pregnant, I would often lie awake at night and wonder how I could possibly love another child the same way when the intense love you feel for your first is so all consuming. But you do and seamlessly, the heart just expands and makes room for more.”