Have you ever wondered why newborn babies often fall asleep while feeding from the breast but not from the bottle? Is it the warm comfort of the breast? Or because they can't see the milk in your breast, so they lose interest?
None of those explanations is true. The answer lies in the flow of milk.
Babies, especially newborns, are "flow-dependent," meaning they need a steady flow of milk in order to keep feeding. If the flow slows down, they slow down too.
When as a new mom you have your initial let-down, your breast muscles contract and squeeze the milk out at a faster rate, which makes feeding your baby a breeze. However, after the let-down is over and your baby has drained the milk from your breasts, she has to work harder to suck more out. Many newborns don't have the energy to keep going and fall asleep instead, often before getting a full feeding.
A bottle has a steady flow of milk from start to finish. Babies don't usually slow their rate of drinking or fall asleep when they feed from a bottle.
Breast: Each breast has nine to 15 nipple pores, so the milk flows out like water from a showerhead. That's why a deep latch is so important.
So how can you make sure your baby doesn't fall asleep at the breast before she's filled up? By increasing the flow rate using the following simple methods:
Pull your baby in closer to your breast, then with your other hand squeeze your breast to hand-express some milk into her mouth at a steady rate. This will wake her up a bit and remind her of what she's supposed to be doing.
When your baby latches onto your other breast, she's getting a whole new reservoir of milk, one where the flow rate is faster. This is because let-downs are simultaneous—while your baby was drinking from the first breast, your milk was pooling in the other one. You can switch breasts 3 or 4 times per "meal" to help your sleepy newborn get a full feeding.
When your baby is a few weeks older and a more experienced feeder, the flow rate is less important because she'll have a stronger suck and can stay awake longer.
Source: Heather Kelly is an International Board Certified Lactation Consultant (IBCLC)