I'd heard this claim before, and never gave it much thought. The Mosaic law was much harsher and less civilized than what Jesus gave in his time, and what most civilizations have adopted. The Mosaic law called for harsh punishments, even death, for offenses that are no longer regarded as nearly so severe, such as working on the Sabbath, or rebelling against one's parents. It's entirely believable that under the sort of dealings that God saw fit to have with the Israelites in that time, that a child might die because of his mother's sin. It makes me think of how David's first child by Bathsheba was condemned, because he was a product of adultery and murder. It's difficult for us mortals to really understand, but in that case, it wasn't the innocent child that was punished, but the child's parents, for the grave sins that surrounded that child's conception. The child is in Heaven, with God, having died sinless.
But you're right, and the article that you cited is right. A reading of
the relevant passage in the KJV gives no hint at abortion or miscarriage; that is very clearly an erroneous interpolation made later, that has somehow come to be spread and believed by many who haven't bothered to look it up for themselves.