The Celebrity Big Brother star told OK magazine that she and husband Tom Williams are expecting a brother or sister for their two sons Rocky and Striker.
"I didn't know [about the pregnancy]," she said. "I wasn't being irresponsible. I didn't know I was pregnant - now I do, there's no way I'll drink. For one glass, I don't see the point. I don't enjoy it enough. I would never risk my child's health.
"I know the dangers of drinking and smoking while pregnant. I was massively addicted to dieting but the second I fell pregnant, my addiction went out the window because I don't want my unborn child not to be getting enough food just so I can be skinny - it's ridiculous."
The 30-year-old said that she is hoping to add a baby daughter to her family: "I'd love a girl but I'd also be happy with a boy because I love going to the football. But I would love all the ballet and tutus. I love children, I love being a mum and having a big family."
Discussing her surprise at discovering she was expecting, McLean said that she believed her battle with an eating disorder had "blown any chance of having more kids".
She continued: "So I was pretty devastated because I want a house full. But suddenly my periods started coming back, which meant I was getting better. At my worst, I was six and a half stone, under a size four and wore clothes for 8 to 9-year-olds. After all the craziness, I was so worried about the internal damage I had done."
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