https://www.history.com/news/what-is-the-origin-of-the-heart-symbol
generally it actually was simply ornamental, or maybe related to some plants like the ivy as mentioned above... and yes, it is abortifactant like i said
not saying it's the *origin* of it but there are related symbols that more accurately represent the three chambers of the heart, as discussed in this link:
also, i think the most explicitly female sexual version is the one that made it onto playing cards via the Tarot... the original symbol was in fact a chalice, and the wand and chalice are euphemisms used in old writings about sexual conjurations, the spades or swords represent the mind and the disks represents matter