The source article says that "mental and behavior disorders and drug and alcohol induced death contributed to 21.2% of late maternal deaths". It seems clear tha

The source article says that "mental and behavior disorders and drug and alcohol induced death contributed to 21.2% of late maternal deaths". It seems clear that at least some drug overdoses are being counted in the late maternal deaths subcategory. (The article also says "homicide, suicide, and drug overdose are the leading causes of pregnancy-associated death", although they do take care to note that pregnancy-associated is a broader category which statistics don't typically include.)