"I don't know, apparently protection was just thrown out the window!" Simpson told Ellen when asked how her pregnancy came about. "We were definitely extremely shocked."
When discussing her pregnancy, the fashion star revealed her second baby bump wasn't as easy to carry as her first one.
"Like with Maxwell, I felt amazing," she said. "Like, I could do everything, eat everything. Do whatever I wanted. I had a lot of energy. This time around...I'm like, exhausted, eating Tums. That's my snack of choice!"
But it's not all bad. Simpson also said that having had to deal with all the extra weight form her first pregnancy less than a year ago was motivating her to be more mindful about her eating habits.
"This time around I think because I was doing Weight Watchers and I felt super healthy, I'm not really craving as much and I know how hard it is [to take the weight off] so I'm trying to make healthier, wiser decisions," she told Ellen.
Not that weight was ever a problem in the eyes of her fiance Eric Johnson.
"Apparently Eric still wanted me so...I can gain as much weight and I will have a husband-to-be that loves me!"
As for the baby's sex, Simpson wouldn't give Ellen a straight answer. The talkshow host finally forced Simpson to choose between two jerseys for her daughter Maxwell, one read "I heart my brother" and the other "I heart my sister." In the end, Simpson picked the "brother" one.
"You never know," Simpson said laughing. "If it's a girl she might call her bro."