No answers 🙁

I had my 6week pp visit the other day and my OB said they don’t know why I went into labor at 21 weeks . I asked about my cervix, placenta , uterus , progesterone levels . The answer was no for reasons x, y, and z . Going forward they will monitor me a little closer. I am not sure if I am satisfied with everything. I know things just happen but I can’t seem to understand why a healthy women and baby would go into labor for no apparent reason . Anyone have a similar experience? Something I could be missing or should of asked ?