In her first interview since Sadie's arrival, the actress said she did not know what motherhood would be like, but found the cliches about falling in love with the baby were true.
"She's great. She's brilliant," she said. Amy and Brian were thrilled when Sadie slept for six hours, but the next night, when it did not go so well, they felt like fools for thinking it was easy.
Brian, she said, is loving his new role as a dad and is great with Sadie, including changing her nappies. He takes over from Amy when he comes in after rugby and tells her to "head off".
The actress put down her svelte shape at Brian's testimonial dinner in London just five weeks after the birth as a "bit of clever dressing". She admitted her body is not the same as before the pregnancy.
The actress said she worried that she would annoy the former Ireland captain when she unexpectedly went into labour as he prepared for the Six Nations match against England in February.
She said the newborn could have been "a red-carpet baby" as she was at the Irish Film and Television Awards (IFTAs) the night before her dramatic delivery by C-section a week early at Holles Street Hospital in Dublin.
Asked if her husband's head was "all over the place" before kick-off, she said: "I think he can't really remember the first half, which is maybe a good thing."
Amy said she was freakishly calm when she started having contractions at home on her own, but Brian was "just up the road" and jogged down in his Ireland kit.
"We dealt with it, so it all happened, perfectly timed," she told Today FM's Ray D'Arcy Show. "And she arrived and he headed off and played the match.
"It was the one day that everybody was saying, 'Cross the legs tomorrow.' I was laughing, going, 'I know, as if.' And then it did."