Since mifepristone can only be dispensed in a clinic, a medical office, or a hospital (per the FDA), you can bill the HCPCS code for it - S0190. Cytotec is S0191. Bill everything on one claim form, even if the patient came back later for the second drug.
The dx code could be Hydatidiform mole, recurrent pregnancy loss, or any number of other dx depending on the circumstances.
Be careful with the dx because the insurance may conclude that it is an elective termination, which may or may not be covered by the patient's insurance, and the patient may have to deal not only with her own loss, but the annoyance that is a denied claim from her insurance company. I had to deal with my own insurance company who had a separate maternity deductible. It was a bad conversation between me and the insurance company, when I asked the member services person to tell me the definition of "maternity", upon which he said, "pregnant with child", and I asked him to clarify that "pregnant with child" meant "growing a child inside you, right?", and he said "yes" (and was quite puzzled), until I said, "well, I went to the hospital because i was bleeding and my unborn baby was dead, so I don't think that qualifies for an extra maternity deductible". He agreed and they paid my bill.
