I started using a nipple shield with DD right away in the hospital and continued for 4 months. I tried weaning her from it but she didn't seem interested and I figured it didn't hurt anything to use it, so I didn't try as hard as I could have. I had no problem with milk supply and was able to pump 8-10 ounces a day to freeze.
Right around 4 months (about a week ago) she weaned herself from it and we haven't used it since. I've noticed that I have not been able to pump as much and I don't feel like my boobs are full most of the time like I used to. Tonight I only got 3 ounces. Everything I've read said that a nipple shield can lower your milk production, but it seems like not using one has lowered mine. Has anyone ever heard of this? She does seem to get enough during the day. She has gone from eating every 3-3.5 hours with the shield to 3.5-4.5 without it, so I'm assuming she's not going hungry. Although she did eat 8 ounces before bed tonight and last night when she normally eats 5. She seems to be growing but its still another week until her doctor appointment.