At week 40, is a c-section the only option I have if I need to have an early delivery?

No. 40 weeks is full-term, so you don't have to worry about being early any more. If you need to be delivered before labor starts, induction is the term that is used. If your cervix isn't open, you may need cervical ripening which can be done with prostaglandins or mechanically. If it is open, we normally use pitocin (oxytocin). Your doctor should be able to go over all these options with you.