Flanged lips

Why are my baby’s lips no longer curled out on the breast?

When a baby tries to latch onto a full, round breast, the lips naturally roll back from the mouth. When the lips do this, they are said to be “flanged.” This helps create the seal between the baby’s mouth and the breast, allowing the baby to hold the nipple and the tissues behind it in the mouth. After a few weeks of breastfeeding, the breasts are not so full. The baby’s mouth does not have to open so wide, so the lips will no longer be flanged.

A) Describing flanged lips

A two-week old baby breastfeeding. The lips are flanged.

If your baby’s lips are “flanged, it means they curl outward on the breast. Think of trying to bite a big ball. You would have to pull or curl your lips back and away from your teeth, and your lips would be flanged

The baby’s lips should not be folded into the mouth.

If you cannot uncurl the lip with your fingers or cannot lift the lip away from the gum, it is possible that the baby has a lip-tie and the baby should be checked by a qualified person such as a pediatric dentist or a physician-specialist. This is not common.

B) The reason that lips are no longer flanged with time

When the mother’s breasts are full, particularly during the first days and weeks after the milk comes in, the baby’s mouth has to open wide to latch. The lips naturally roll back from the mouth to accommodate the fullness of the breast.

A baby’s lips will not always be flanged (Mills 2020). After a few weeks of breastfeeding, the breast fullness subsides and the breast and the tissue behind the nipple (the nipple root) softens. At this point, the baby’s mouth will not have to open so wide to latch and the lips will no longer be flanged.  

After a few months your breasts feel even less full. The breasts can even feel very soft. Your baby’s mouth will appear to be holding just the nipple. This is normal. It will not result in nipple pain or in the baby not taking in enough milk.

Babies also do not open their mouths as wide after the first month when latching.


Mills N, Lydon AM, Davies-Payne D, et al. Imaging the breastfeeding swallow: Pilot study utilizing real-time MRI. Laryngoscope Investig Otolaryngol. 2020 May 20;5(3):572-579