Absolute first no, but I think I was ~6 when we were watching Four Weddings & a Funeral (which I’d seen before) at a sleepover when it suddenly occurred to my parents to check w/my friend’s parents. (Fwiw violent gore in movies was a Big problem for them, but sex & swearing they didn’t care.)
Do you remember what *your* first R-rated movie was? I finally asked my mom (I couldn't remember), and she told me it was The Lost Boys when I was roughly the same age as my daughter (about 9). The movie traumatized her more than it did me, apparently