In an ideal world a caesarean should not be planned prior to week 39 and, in the UK at least, caesareans tend to be during this week unless there is a medical reason indicating that it should be sooner.
Research does show that by week 39 a baby’s lungs are sufficiently mature to cope well with delivery. Anything prior to 39 weeks increases the possibility of respiratory problems. That said where there are medical reasons making it essential for baby to be delivered prior to 39 weeks then a planned caesarean (where all the facilities and resources needed to make this as safe as possible are ready and waiting) is considered by many practitioners as preferable to inducing labour.
What is really important during the decision-making process is the accuracy of the dating of your pregnancy, if you are unsure then you should request a re-assessment.