Pennyroyal leaves and angelica root are used as menstruation inducers by some herbalists and traditional midwives. Blue cohosh tincture, also used to induce or augment labor by the same groups of alternative medicine practitioners. Menstruation induction is essentially a euphemism for early abortion in this context, even if it can be carried out by women who are not actually pregnant as well sometimes. Some of these herbs are said to be extremely effective. Others might or might not work in concluding a miscarriage, and could cause very serious damage to a fetus if the miscarriage (abortion) is incomplete. Herbal abortions were once widespread as was herbal birth control, curiously enough, even permanent birth control and used by many ancient cultures including among Native American tribes, in Africa, In Traditional Asian Medicine, and by European granny midwives or "witch doctors".
Herbal abortions must have worked for these traditional folks, but in this day and age safer and medically monitored abortions are available. Whatever your stance on abortion (and whether we are pro-life or pro-choice, nobody likes abortion, let's face it), you probably have to acknowledge that modern medical abortions are a lot safer and more effective than herbal abortions or menstruation inductions. If you are facing a situation in which you are considering this for yourself, the first step is thinking about your safety. Realize that even with a herbalist at your side, such measures are not regulated by anybody and could prove to be very dangerous, and not only for your fetus. Herbal medication can have side effects that are less documented than regulated drugs, and can cause liver and kidney failure for some, for example.