There are two groups that this is problematic for - users of illegal drugs and women. Society may not like it that people use illegal drugs, but that doesn't mean that we can make up evidence and not rely on the facts. Women who use illegal drugs do give birth to healthy babies. (They also often give birth to low birth weight babies with all the problems that ensue from that).
In this case, a woman who was a drug user had a still birth, but they do not have good evidence that the drug use was the cause of the still birth. Many women who have not taken drugs or participated in any kind of risky behaviour have still births and miscarriages. The woman who used drugs may have had a still birth even if she had not taken the drugs. Yes, meth is illegal, but the crime she would then be guilty of is possession of illegal drugs, although really there should be patient confidentiality so that addicts get treatment, and cases like this shouldn't be brought.
As for the contraceptive argument, women who use illegal drugs are not all incapable of bringing up children or or having healthy pregnancies, so it their choice if they decide to get pregnant or continue a pregnancy after not intending to conceive.
As for women as a group, it is not in anyway similar to killing of separate people in society. Everyone in society has a power to not make choices that harm others by our actions when we choose come into contact with them. That is part of our understanding of the autonomy of other people. We don't need to punch other pregnant women, feed them dangerous food or contaminated water, rent them houses with carbon monoxide problems etc. That is entirely separate to people making choices about their own bodies, and by extension people who have to make choices about a body they are sharing with a foetus. Sharing a body with somebody else is an incomparable situation to hitting or poisoning a pregnant woman or newborn baby you have the choice to walk away from and not interfere with. You don't have the choice to walk away from a foetus unless you are aborting it.
Unless somebody has such severe mental health problems that they are rendered delusional and are incapable of assessing risk, the risks a woman is prepared to put her and her foetus through together should be her choice. The question of whether or not this issue will lead to women being charged with manslaughter for being fat, for living in damp housing or for eating cheese is a serious one. I don't know exactly how risky it is to a pregnant woman and foetus to take various illegal drugs. The assumption that it is riskier than obesity, damp or consumption of various foods is a prejudice against drug users and a desire to deny them rights, which could have huge consequences for other groups of women that governments want to target. Drug use may or may not be riskier, but we need to see evidence of that. There has been some very prejudiced reporting in the media of obese pregnant women and the danger to their babies. I would see obese and overweight women as being vulnerable to these kind of manslaughter laws.