I've come across one case of probable infanticide so far (unfortunately my GG-grandmother* was involved in the cover-up). The child was born to an unmarried girl, though, not a married couple. The mother and grandmother were found not guilty, because the pathologist said he couldn't be 100% sure it wasn't a natural death, but I don't think there was much doubt about it, otherwise there would have been no need for a cover-up:
https://magazine.familytreeforum.com/?p=63.
* Actually she turned out not to be my GG-grandmother at all, but I thought she was when I wrote the article. Her son was my grandmother's mother's husband, but turned out not to be her biological father.