Hi,

Pumping before your baby is born is working against nature. High levels of progesterone in the body work to suppress lactation. You just won't get much. Pumping will be a very dry argument.
As others have mentioned, in some specific cases it may be likely that babies may need a little more colostrum than would be normally available in the first hours after birth. Under advice from their health care professional some mothers hand express (not pump) to get a few more mls which might be enough for their baby to avoid the need for articifical supplementation with all the problems that can cause.
Antenatal expressing won't induce labour until your cervix is *ripe* ie there are oxytocin (the hormone which is released when your milk lets down, and also with orgasm and other pleasurable experiences) laid down. This doesn't happen until birth is imminent anyway.
There is a way to get a headstart on breastfeeding - but it has everything to do with your brain and little to do with your breasts. Go to an ABA Breastfeeding Education class. Learn how breastfeeding works - it's a simple and predictable system. But to most in our culture it's a mystery. It doesn't need to be. learn about the impact your birth has on breastfeeding; make a plan for breastfeeding that will make it work for you