The moon tea that Alicent drinks and its effects mirror herbal remedies, often teas, used in our own world to induce miscarriage. These have been used for centuries to various effects, though it’s important to note that some of the herbs can be extremely toxic in the wrong doses and can lead to death. Many of the herbs used in these teas are also used to stimulate menstruation and have other holistic properties, though they have not been widely studied in the medical and scientific community (and most herbalists with the knowledge aren’t willing to talk about it). These medicinal teas are an underground secret still, just like they were in the medieval era that Martin draws inspiration from. 

Fans of the grunge band Nirvana might recognize the song “Pennyroyal Tea,” inspired by singer Kurt Cobain’s friends trying to use a tea made from pennyroyal, a herb in the mint family, to induce abortions. (It’s important to note that while pennyroyal is safe in small doses and has holistic uses beyond its abortive properties, pennyroyal oil, sold in aromatherapy shops, can kill you dead in even the tiniest amounts!)

In an ideal world, people would be able to have full bodily autonomy and have the proper care for all of their reproductive needs. But since neither our world nor Westeros are ideal places, there will sadly always have to be sketchy underground alternatives.