"Since there were not, and still are not, any statutes on the books specifically criminalizing drug use during pregnancy, women have been prosecuted under statutes that deal with child abuse, assault, murder, or drug dealing [150]. One of the newest attempts in prosecuting women is using statutes related to the delivery of drugs to a minor. However, it is much more difficult to convince a judge and jury of prosecuting on these grounds because there is no explicit language in any statute delineating that a fetus can be considered a minor, entitled to all the rights and privileges afforded thereto [151,152]."

Source

Lester, B.M., Andreozzi, L. & Appiah, L. Substance use during pregnancy: time for policy to catch up with research. Harm Reduct J 1, 5 (2004). doi.org/10.1186/1477-7517-1-5.