It is a common assumption that a caesarean section is always performed when there is a multiple birth situation. However, it is a common myth that all multiples are born via c-section. There are cases where the birth of multiples has happened naturally. However, there are numerous risks associated with giving birth to multiple babies.
The chance of having a c-section is increased with the addition of more babies. The more children you are having, the more likely you will end up in an operating room instead of a birthing one. However, there are plenty of obstetricians willing to attempt a vaginal birth first if the risks are minimal. If it looks like mum and both babies are in no danger, then it hardly makes sense to rush into a caesarean without cause.
However it is true that c-sections for twin births have increased in the past three decades. The assumption is that many doctors have resorted to using caesareans automatically in multiple birth situations to avoid any potential complications. If a vaginal birth is what you truly want, then it is best to consult with doctors beforehand to find out which ones are more willing to try a vaginal birth for twins.