What you don't seem to get is no one is arguing with you about that or defending the "POS" woman, pregnant, with a needle in her arm.
The question is what to do about that woman. We arrest drug users and dealers, fill up the jails, spend $25k/year housing them, and what do you see next time you go to the shooting gallery? A bunch of drug users, probably a bunch of them that have made the round trip to jail, back to the streets and back on drugs. Same with the dealers. So that approach seems to be working out great, if you've got an interest in jails and make more money when they're full, but not so great for the rest of society.
But sure, if you see a pregnant woman on drugs, run her in and keep her locked up and clean till she gives birth. No one suggests forgiving her sins and letting her continue to use while pregnant. But if you tell her, "come in and get some prenatal care, and if you have drugs in your system you'll be charged with manslaughter, your baby put in foster care or up for adoption, and you'll spend 5-10 years in jail," do you think she'll come in? Not likely.
The only thing I'd like to see is a little of that 25k/year spent housing addicts get diverted to treatment and maybe you'll get a few women cleaned up and next time they get pregnant they won't be using during it, and those with kids will be able to take care of them instead of taxpayers doing it. Or we can build some more prisons and extend our lead as NUMBER ONE!! in the world in prison population, both in nominal numbers and per capita. "Working great, especially with drugs, so why not continue it," says the for profit prison industry.