Connecticut Subscriber Answer: A missed abortion means that the baby died in utero, there is no heartbeat, and the ob-gyn induces the delivery or the expulsion of the fetus or removes it surgically. Generally, the physician performs a dilation and curettage (D&C) to remove the fetus and the products of conception. This is what is included with 59820 (Treatment of missed abortion, completed surgically; first trimester).
In the case of an incomplete abortion, the fetal tissue has basically passed already and there are still retained products of conception, so the patient continues to bleed. You should use 59812 (Treatment of incomplete abortion, any trimester, completed surgically) when the ob-gyn goes in and scrapes out the lining but some of the products have already been expelled. Of course the diagnosis codes will be different. You should use 632 (Missed abortion) for a missed abortion, which will be the match to 59820, but for the incomplete abortion, you will use 634.9x.