Generally they're for short term use for the reasons outlined above - they can interfere with the supply and they don't help bubs to learn how to attach to the breast well without help.

If a bad attachment has been allowed to go on they provide incredibly valuable rest while the nipples heal (though with a correct attachment the nipples can heal even WITHOUT shields), and for some babies (like those with tongue-tie) shields bridge the gap between birth and being ABLE to form a correct attachment. I think the main reason they are worried about is that some people never get a good attachment because they use the shield and without proper support don't learn how to attach and then try without, get injured nipples again, go back to the shield, etc. etc. until pretty soon they lose their supply or give up in agonised despair.

For the first few weeks milk production is driven hard by the pituatry gland AND by the stimulation at the breast (which is why most people have masses for those early weeks then it tailors to bubs need) and generally shield use during that time won't have too much impact, but past 4 or 5 weeks supply begins to tailor just to demand so it's good if bubs can be attaching themselves by then.

If i were you Gracie i'd get a LC to come out to you and have her help you practice the attachment without the shield, but hang onto it so you can always use it if you need to when she isn't there. I do know a woman whose little girl just couldn't get to grips with it and she used shields until her DD was six weeks old, by which point her mouth was bigger and she could feed without injuring her long-suffering mum. This did her no long-term harm and the mum was able to BF for as long as she wanted to.

Don't feel disheartened Gracie, every day is a year in terms of learning for bubs - you'd be amazed at the difference even another week of practice at this living, breathing, sucking lark can have. You're doing a great job, hang in there.

Bx