Discussing the possibility of becoming a mum, the 39-year-old said due to her family's history of cacner, she wouldn't want to risk it.
Riley's mum died from breast cancer ,aged 57, and her father had a cancer scare in 2015.
"With my gene pool, it wouldn’t feel fair having a child myself," she told OK! Magazine.
"I think I'm more likely to adopt from one of the countries I’ve visited - Ethiopia or South Africa - than the western world."
The actress has previously spoken publicly about her reticence to start a family.
In November 2013, following her mum's death, Riley said, according to the Mirror: "I can’t see myself ever becoming a mum.
"I wouldn’t want my child to endure the same agony I have endured since mum died of breast cancer."