C.E.
Same thing happened to my daughter at about 4 mos as well. When I spoke with my Lactation Consultant, she said that at this age, sucking is a "choice" for the baby, so the baby may choose not to suck on the bottle (preferring, and holding out for, the breast). We tried different bottles and nipples to no avail. Finally, I just had to give her the bottle myself (my husband gave the bottles) until she started taking it again. My husband also started giving her the bottle while she was in the high chair vs holding her in an "arm cradle," which is closer to what her position is when breastfeeding. I think it took a few weeks before she stopped refusing it. She started daycare at 6mos and has had no issues with who give her the bottle since (or breastfeeding when it's me). I noticed at daycare, that the providers hold the babies "facing out" as well, which may have made a difference.