I find it a little bizarre that there is still an attitude that women using herbs to control their fertility is somehow 'unnatural' or not good.
European women were stripped of their indigenous knowledge of herbs, child-bearing and fertility during the witch-hunts, which removed both the witches and their folklore, making women vulnerable to control by the church and state who were in need of higher populations of workers in order to bolster the new mercantile economy.
"The attack of church and state against the witches was aimed not only at the subordination of female sexuality as such, although this played a major role, but against their practices as abortionists and midwives... Not only were women artisans pushed out of their jobs and their property confiscated by the city authorities, the state and the church, but women's control over the production of new life - that is, their decision to give birth to a child or to abort - had to be smashed. This war against women raged throughout Europe for at least three centuries" - Maria Mies, Patriarchy and Accumulation on a World Scale.
Other cultures worldwide have managed to hold onto their traditional indigenous knowledge of fertility and herbal medicine and their control of fertility often goes unnoticed.
The problem is as stated elsewhere on this thread, when unempowered women try to make random choices about fertility and end up with a big mess - either an unwanted pregnancy, or a damaged fetus from the inconsistent or improper use of abortifacients, or possible health complications to the woman from uneducated use of herbs or vitamins.
Large doses of Vitamin C are effective - which is why many pharmaceutical companies sell Vitamin C with rosehip added, which counteracts the abortifacient, as they didn't want to be associated with ending pregnancies.
I second Sister Zeus as an emergency source of information on emmenagogues and abortifacients.
I also second any recommendation which gives more empowerment, information and agency to women to make these decisions about their own fertility in ways that are self-loving, responsible, and safe.