The woman in question, whose case has appeared in local media, asked that her name be withheld. She is post-menopausal, married to a man who is 38, and became pregnant with a donor egg. She is due in November.
"I had already gone through menopause... My husband wanted to be a father. I wanted to be a mother too. I am in great health... and I have undergone a very thorough medical clearance," she told O Globo newspaper.
She said she did not plan to tell her future daughter about her having used a donor egg to become pregnant.
It is not Brazil's first late-in-life pregnancy. As recently as September 9, a 52-year-old woman whose husband is 88 became a first-time mother of twins.
Brazilian health officials say they are concerned about a wave of late-in-life pregnancies, which can put great strain on and harm some older mothers' bodies.