When possible, wait to introduce a bottle until breastfeeding is going well. It takes time to master breastfeeding, and your body needs to establish a good milk supply. Solely breastfeeding the first two to three weeks helps get breastfeeding off to a good start.

But don’t wait too long to introduce a bottle. Plan to take advantage of your baby’s sucking reflex. Babies are born with many reflexes, like grasping a finger or turning their head toward an object that brushes their cheek. Sucking is also a newborn reflex. Babies suck for nourishment, and they suck for comfort.

As babies grow, many of their reflexes diminish. Sucking is one of the reflexes that changes from spontaneous to voluntary. A young breastfed baby will reflexively suck on a bottle. An older breastfed baby will often refuse to suck on a bottle—he or she chooses to suck on mom—breastfeed. In other words, sucking becomes voluntary. Most babies still have the sucking reflex at 3-4 weeks of age. A few babies have this reflex a bit longer, but it begins diminishing around 4 weeks for many babies. Introduce the bottle while your baby’s sucking reflex is still present. In my experience of working with moms and babies, bottle introduction during the baby’s third week is ideal. If you miss this window-of-opportunity when your baby is willing to suck on anything, bottle introduction may be met with resistance from your baby.

One exception of waiting to introduce a bottle is when a baby is not breastfeeding well in the early days. A bottle can be used to provide nourishment until the baby learns to breastfeed. The bottle is used as a tool to work toward breastfeeding. Pumping with a high quality pump during this time establishes your milk supply and allows you to put breastmilk in the bottle.

There are a few babies who love to suck on anything and everything, and switch easily between the breast and any type of bottle. I call these magic unicorn babies. These babies do exist! But most babies are not this easy going and will show a strong preference to only breastfeed. Rather than crossing your fingers and hoping that you have a magic unicorn baby, safeguard your baby’s acceptance of a bottle and introduce it around 3-4 weeks of age.