Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Nipple too big for newborns!

We brought these nipples based on all the raving reviews and write up's online. However our newborn is now here and wasn't putting on enough weight. Our pediatrician told us these are the worse brand of bottles on the market for newborns and shouldn't be used until the baby is at least 5 months old. The reason for this is because the nipple is too large for a newborn to latch on to and they're unable to get enough. We are now using the Medela nipples instead and he's feeding so much better.