The Shameless star, 50, and her husband Paul Chase - who is 19 years her junior - conceived following egg donation.
Tina - who is just five weeks into her pregnancy - announced her news on This Morning saying:
"I am pregnant. We are delighted.
"I think it's important that I'm much more healthy than I was 20 years ago. I've had ECGs, I've had blood tests, we've had everything done. And physically, mentally, emotionally, and even financially, believe it or not, I'm better than I have been for 20 years. And I've got the best man or partner I could ever have.
"I have a beautiful, wonderful talented daughter but it would be just so nice for us to have a baby. We realise it's early but it would just be so nice. But we are aware there can be pitfalls, we are only five weeks, and we're ready.
"The more relaxed you are with IVF and the more positive you are the better."
Speaking on the show, Tina - who had daughter Danielle when she was 17 - added that there are signs she is carrying twins.
"I've got indigestion already, which indicates a girl, but I've also put about eight pounds round my back in four weeks so that indicates a boy," she said.
"So fingers crossed we're having twins and it's a boy and a girl. I would be ecstatic, absolutely ecstatic. I would just write books and cook and bring my babies up."
Tina was fitted with a gastric band in 2010. Speaking about her pregnancy plans on This Morning last year, she said she would be keeping her gastric band in place during her nine months: "I will probably be one of the most unique women keeping the gastric band, it has to be loosened to enable the baby to get enough nutrients.
"But it doesn't affect it. The womb and the intestine are completely different organs and compartments in your body."