I had one with #3, woke up the next morning in labour, she was born 49hrs later.

Had one with #6, did nothing but made me lose my plug.

Had one with #7, had LOTS of regular contractions that day and intermittent strong ones over the next week, also had lots of increased mucous and lost my plug. Ended up being induced 8 days later but when i had the sweep done my cervix was long and closed, when i was induced i was 3cm, stretching to 6cm. So it did something over the course of that week.