The UK Telegraph reported that Mrs Carter, from Indiana, met Mr Bailey four years ago after he tracked her down following the death of his mother, Lynette.
Mrs Carter fell pregnant with Lynette at 18, out of wedlock, and claims that she was forced to give her child up for adoption by her strict Catholic parents.
She went on to marry, but never had any more children.
The couple, who claim to be abused in public and could face prison for incest, say that they fell in love and became lovers soon after meeting.
In an interview with the New Zealand magazine, New Idea, Mrs Carter, said: “I’m not interested in anyone else’s opinion.
“I am in love with Phil and he’s in love with me. Soon I’ll be holding my son or daughter in my arms and Phil will be the proud dad.”
Mr Bailey said: “I love Pearl with all my heart. I’ve always been attracted to older women and I think Pearl is gorgeous. Now I’m going to be a dad and I can’t wait.
“Yes, we get laughed at and bullied when we go out and kiss in public but we don’t care. You can’t help who you fall for.”
Mrs Carter said that she searched for her lost daughter for many years, finally giving up hope 15 years ago. After Mr Bailey’s mother died from cancer, he decided to find his grandmother, finally tracking down her address and writing to her.
Mrs Carter, who was then single, said: “I was stunned to get his letter. My heart jumped that I’d be re-united with a grandson.
“When he emailed me a photo, I thought what a handsome and sexy man he was before pinching myself – he was my grandson. I wrote back immediately and included my phone number.
“From the first moment that I saw him, I knew we would never have a grandmother-grandson relationship. For the first time in years I felt sexually alive.”
Mr Bailey, a carpenter, said that he too felt instant attraction towards his grandmother. He said: “I wanted to kiss her there and then. My feelings were overwhelming.”
After a night out during their first week of dating, Mrs Carter decided that she would no longer hide her feelings from her grandson.
She said: “I called Phil into my bedroom, sat him on the bed, and then I leant over and kissed him. I expected rejection but instead he kissed me back.
“Living with Phil as my life partner has been amazing. He cooks and cleans and we make love three times a week. We can’t keep our hands off each other.’
A year ago, Mr Bailey announced that he wanted a child. Mrs Carter told him she was also desperate for a baby, but it was one wish that she could not fulfil as she had already gone through menopause.
The couple then decided to use Mrs Carter’s retirement money to find a surrogate mother and buy a donor egg to inseminate with Mr Bailey’s sperm.
They placed an advertisement asking for an open-minded surrogate, and Roxanne Campbell applied.
“Initially I was shocked,” said Miss Campbell, on learning the couple were related. “But they’re a brilliant pair and I saw how much they loved each other. I know the baby will be loved too.”
The couple sees Miss Campbell, 30, once a month and accompany her for scans.
Mrs Carter said: “I am just so happy. I am finally going to be a mum and not forced to give up my child.
“Phil’s going to be a great dad. I never in a million years thought at 72 I’d be ‘pregnant’ and in love with my grandson. I make no apologies and I believe God’s given me a second chance.”