In Medieval England, the age of viability was 6 years old based on how much work the child could do. Before that, it was legal to infanticide your own child.
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this is not true.
Yes it is true.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1082157/pdf/medhist00104-0005.pdf
https://www.karger.com/Article/Abstract/441275
https://press.uchicago.edu/books/TheChild/Child_pages_1-10.pdf