Pros:
- they can reduce pain and trauma to the nipple
- if you have a baby who is used to bottles or who will not latch onto the breast due to flat or inverted nipples, a shield can help that baby latch onto the breast
- modern thin silicone shields are less likely to cause supply reduction than older, thicker shields
Cons:
- shield use can reduce stimulation to and milk removal from the breast, causing feedings to take longer and be more frequent, and potentially causing reduction in milk supply
- shields are unwieldy, particularly in public (imagine having your shield fall on the floor in a grubby public location, and not having another in your bag...)
- babies can get hooked on the shield, meaning you end up using it long after you need it
Basically, shields are best used when you have a baby who resists latching for some reason. In that situation, getting the baby to the breast is more important than the considerations of unwieldiness or milk supply. Using a shield for hurting nipples isn't ideal, because a latch that hurts is sometimes a latch that isn't so great at getting milk out of the breast, and the shield can make getting milk even harder and lead to reduced supply, to boot. If you can, see a lactation consultant (preferably an IBCLC) before resorting to shield use. Perhaps your baby's latch can be fixed without the shield. And if not, then the LC can give you guidance on how best to use the shield without risking your supply.
Of course, if the shield is the only way you can continue to nurse, by all means try it!
The previous poster brings up all of the best points. I'm not sure what the risks would be as far as the baby getting nipple-confused (we introduced a bottle at 2 weeks despite breastfeeding not having been established yet)....but I would consider how well your baby transitions between breast and bottle...
I will say that having had to use a nipple shield for the first month of breastfeeding -- if there were any risks of getting "stuck with it", I would not take the risk.
They are messy and a pain in the butt. Using them in public is awfully difficult and if your baby can not nurse without it you can really be put in a pickle.
Personal story: I was given one nipple shield by the LC at the hospital to take home with me...and when my boy was about two weeks old MY CAT ATE IT!! My son could not nurse without it, so I sent my husband to the baby store to get a new one and he came back with a breast pump flange! I then left him with the baby to correct the mistake, I should have known to have a second one on hand.
Jack, my nursling (Oct 2015) Kevin, my preschooler (Mar 2012)