The dynamics of both his relationship with his wife and her subsequent illness are based on Ted's wish to have a child of his own. Although he is very close to Stella, Stella is uncomfortable referring to Ted as "Dad" or anything similarly familiar.
As Stella described to Dr. House, Margo never fought with anyone, particularly Ted, although Stella was aware that most of their discussions revolved around having another baby. Because it appeared that Margo was having difficulty getting pregnant, she agreed to take fertility pills to increase their chances. However, as Dr. House noted, Margo already had a busy life between her husband, daughter and career. He guessed that Margo was sabotaging her fertility by also taking the pill at the same time to prevent her from getting pregnant. This flood of hormones caused a benign hepatocellular adenoma, House wanted her to just stop taking hormones (at which point the adenoma would start shrinking), but she denied being on the pill.
However, after the surgery, it was clear that Margo had been taking the pill. She begged Eric Foreman to tell Ted that she couldn't have anymore children, but he refused to lie for her. House told her to tell Ted, but she said she would just go back to doing what she did and hope he would forget about it.