Pearl Carter and Phil Bailey, 26, have paid a surrogate mother £20,000 to have Mr Bailey’s child, which the couple plan to bring up together.
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.”