The BMJ has an entire issue discussing infanticide.
There are a few with fuzzy arguments why this is wrong.
None seem to have a religious argument (such as "Well, the Lord God said it was a no no to kill your babies" (this one dismisses religion as being against "questioning" things, therefore we need to discard all religious arguments, and then dismisses what he thinks their arguments are, not what religions actually believe.)
"Every murder or other injury, no matter for what cause, committed or inflicted on another is a crime against humanity."
of course, they use a "hat trick" by redefining murder as the killing of a person, and then redefine who is a person according to their own ideas.
The problem? Who died and made them king? Why do we allow these people the "right" to remove the right to live from huge segments of humanity?
Hannah Arendt in her book Eichman in Jerusalem actually predicted this would happen, that in the future experts will devise criterias for personhood and then arrange to kill those who don't meet the criteria.
all of this reminds me of this song: