Wollstonecraft & Shelley

I recently finished reading a biography of Mary Wollstonecraft and her daughter, Mary Shelley. The book is somewhat histrionically titled Romantic Outlaws but, given the unorthodox lives that both Wollstonecraft and Shelley lived, histrionics don't seem altogether unwarranted. 

Wollstonecraft died only 10 days after Shelley was born, so chronologically their lives did not overlap for long, but Charlotte Gordon alternates the book chapters between mother and daughter, which highlights the influence of Wollstonecraft's legacy on Shelley's life.  

For some reason, though, I was particularly struck by a peripheral tidbit about Wollstonecraft's relationship with William Godwin, Mary Shelley's father:

They relied on the birth control system of the time: no sex for three days after menstruation, and then, since everyone believed that frequent intercourse lowered the possibility of conception, a lot of sex for the rest of the month.

Given that she was using this method: 1) with a man who was not her husband at the time, and 2) while already the unwed mother of a small child, this seems like utter lunacy to me. Couldn't she put together that sex = babies, and therefore more sex = more babies? People had been reproducing for thousands of years by 1797—had no one figured this out?! Even blood-letting seems more logical.

In any event, the book achieved exactly what I imagine the author wanted: I am now in the process of reading Wollstonecraft, and I have every intention of finally getting around to finally reading Frankenstein, too. I am overdue for both, but particularly Wollstonecraft, given that she's the only female political theorist of note born before 1900. I avoided reading her because I assumed she was added to the canon only because she was a woman. While I still think this is probably true, I've realized it doesn't matter much. She wrote the first modern argument for women's equality, and it's possible that only a woman would have written such a book.