[MRM]

The serious answer to this question is that it depends on the law of the state where the crime took place. Murder is a state offence and each state has a statute that defines murder in the various degrees. There is no national law against murder, just as there is no national law against assault or driving without a driver's license. The states are free to define murder however they chose.

In some states killing a pregant mother would result in two counts of first degree murder. In some states it would be considered murder of the mother and the illegal death of a fetus as a subset of murder. In other it would be murder and a variation on manslaughter. I don't know of any states off the top of my head where any of the scenarios above would not be some form of murder or manslaughter. A pregant woman overdosing and killing her unborn child but not herslef is pretty classic texbook hypothetical manslaughter, again depending on that state's specific law.

A drunk driver killing a pregnant womand and the unborn child would be criminal vehicular homocide (CVO). In most states it would be two counts with no distinction made for whether the death involved an adult or unborn child.