Mayweather took to Facebook and Instagram to share a sonogram image appearing to show two fetuses.
"The real reason me and Shantel Christine Jackson @missjackson broke up was because she got a abortion, and I’m totally against killing babies. She killed our twin babies," he wrote as a caption to the image.
He has since taken down the image and comment from both accounts.
Mayweather and Jackson broke up last year after he had given her a $10 million engagement ring.