Yes... now you asked Morgana so you gonna get the long answer.
How does the abortion pill reversal process work?
Within 0 -72 hours after taking mifepristone (the first pill), a woman can be prescribed a treatment of progesterone to hopefully counter the effects of the mifepristone. It is most effective in the first 24 hours.
Mifepristone binds to progesterone receptors in the placenta and uterus and blocks progesterone from binding, preventing the normal effect of progesterone on the fetus. If the body is flooded with progesterone, the idea is that the higher levels of progesterone will out-compete the mifepristone for the binding spots.
The progesterone regimen is usually continued for the rest of the first trimester.