Most herbal aborticants are basically "toxin that strangles the internal organs involved in babymaking."
The problem is: they don't stop at those organs. And they don't damage them just enough to cause an abortion.
(There are two main categories: emmenagogues, which stimulate blood circulation in a way that stimulates menstruation, and oxytocic herbs, which cause uterine contractions. Pennyroyal's in the first category. Don't let the innocuous description fool you into thinking it's safe; changing the way the body's blood flow works can and does kill people.)
Most bodies are built to prioritize the fetus over the mother. They draw nutrients from the mother - strip her calcium and iron and vitamins - and work very hard to shield the fetus from external damage.
Trying to scramble that system enough to end a pregnancy without ending the person is a very, very fine line to balance. And, as herbs are unregulated medicine, there's no way to be scientific about it. You can't measure the dosage. Hell, even if it's plants you grew yourself... this one got a little more sun; that one got more of the western breeze; this other one got more water when it rained because it's closer to where the puddle forms. And so on.
Herbal aborticants are like applying a tourniquet to stop the bleeding... only you can't see where you're tying it off, can't tell how tight it is, and can't release it when you want. Sometimes it works; sometimes it doesn't; sometimes it kills you.
There are going to be women desperate enough to try them anyway.
...essential oil extracts is NOT the way to go for these. "Concentrated poison at a dosage you know nothing about" is a BAD form of treatment.
Pennyroyal tea has a long history as an herbal aborticant. As mentioned, it's dangerous. It kills people. And it doesn't always work. There's no reliable info on how much, how often, what the warning signs are for "this is not going to work for you." But there's at least a long series of anecdotes and history of use in medicinal herbalism. There are suggested doses. (No, I'm not giving them; do not take medical advice from strangers on the internet.)
Pennyroyal is especially dangerous for people with kidney conditions.
Essential oil has none of that history. All you know is "it's the concentrated version." You don't even know if it's the concentrated version of the right chemicals. You don't know which parts of the plant are enhanced.
And essential oil of pennyroyal is fatal-toxic at small doses.
Herbal abortions have a success rate of somewhere between 20% and 75%. There are no good statistics, in part because the women who use these methods often use them before they have verified pregnancies.
If you're desperate enough to be looking at these methods - PLEASE do some real research first.
Don't take medical advice from a Twitter meme.
almost all women report at least one of the following side effects: Increased bleeding, dizziness, nausea, visual disturbances, sweats, chills, diarrhea and that less commonly reported side effects were incomplete abortion, irregular cycles for 1-3 months, kidney irritation and breast lumps
---from a study done by herbalist Collette Gardiner
I'd say, "DON'T use these methods," but... there are going to be people desperate enough to try, just as there were before Roe. We have better info sources now - go find them.
If you can't find medical info about a particular approach - assume that it's made up by Some Asshole Online who wants to kill people.