Yes, after the abortion, hCG levels will decrease until they become undetectable. This will take about 3-6 weeks. For this reason, if you take a pregnancy test during this period, you may still test positive even though you have miscarried.
However, it is important that the hCG values after the miscarriage are decreasing. Otherwise, it is possible that there is still embryonic tissue inside your body and the specialist will have to assess whether you need some kind of treatment.