They arrested an addict whose drug use may have led to a miscarriage, or who may have just had a miscarriage completely unrelated to the drug use, or a mixture of multiple issues.
There is no difference between this and obesity, alcohol, smoking, or poor diet. Obesity has a voluntary aspect to it, and increases your chances of miscarriage. Eating non-nutritious foods, micro plastics, not taking prenatal vitamins can all contribute to miscarriage. Getting into a car accident while voluntarily driving while pregnant, staying with a violent husband who beats you while pregnant... I mean where do you draw the line at making the pregnant woman 100% responsible for anything that happens while she is pregnant?