No one can detect if a woman has had one or more abortions, because it does not leave any traces. Pregnancy itself does leave traces, however. The pregnancy hormone Beta-HCG dissipates slowly from the body, and a pregnancy test can still be positive up to 4-6 weeks after.
If you have a medical abortion using the drugs mifepristone and misoprostol (or misoprostol alone), the effect is like a natural miscarriage, and it is impossible for a doctor to tell the difference. The drugs are metabolized within 24 – 48 hours and would not be detected in any conventional blood test.
Even if you have complications such as infection or retained tissue, these can occur just as commonly in a miscarriage.
The only time a doctor may suspect that you’ve had a previous abortion, is if you had an unsafe abortion in which you suffered serious complications that left scarring or other signs of permanent injury to your uterus or cervix.
Women on Waves, Misoprostol, abortion pill, cytotec
Dr. Aarti Abraham (Health Care Magic), Can mifepristone and misoprostol be detected by blood test? (2013)