Causes of slow growth

Why is my baby not growing well?

If a baby is not growing well, it’s because the baby is not taking in enough milk or the baby is sick. In either case, mothers should work with their health-care providers to figure out the problem and ensure the baby is fed. If a baby is not getting enough milk, it may be because the mother has a low milk supply or the baby is not breastfeeding enough or effectively. Tools such as expressing or weighing the baby before and after feeds can help identify the problem. Underfed babies will gain quickly if given extra milk.

Consider using our quick assessment tool, “Why is my baby gaining poorly?” to guide you through this concern.

A) Reasons for poor growth

This baby boy’s mother had had breast reduction surgery and was unaware that this was likely to affect her milk supply. Until supplements were started, the baby was breastfeeding very often, generally unhappy, and thin. After starting supplements, the baby had a normal feeding pattern, was happy, fleshy, and gained well.

The most common reasons for a baby not to grow well are as follows:

  1. The baby is not taking in enough milk because:
    1. The mother has a low milk supply.
    2. The baby has poor access to the milk because the baby:
      1. Is not breastfeeding often enough.
      2. Is not feeding effectively.
  2. The baby is sick.

The quality of milk is rarely a cause. 

When a baby is not growing well, health-care providers may say the baby is “failing to thrive.”

B) Managing babies who grow slowly

If your baby is not growing well, please work with your health-care provider to:

  1. Ensure that the baby is fed.
  2. Figure out the problem.
  3. Try to fix the problem.

Some causes of poor weight gain are obvious. For example, mothers with very poor milk signs or a history of extensive breast surgery are likely to have a low milk supply. Babies who cannot latch or stay latched clearly have breastfeeding problems.

Babies who are not getting enough milk show definite signs such as constant scowling.

Other times, problems can be less obvious or there may be more than one. Sick babies may be difficult to identify as underfed because the signs may be less obvious. Newborns who are not taking in enough milk may be very sleepy and also hard to identify as underfed.

If the cause is uncertain, mothers can:

The following table interprets the results of the these tools. 

Table: Tools to identify the cause of poor weight gain

(Links to more information about the topics in the above table: normal milk amounts; normal weight gain.)

If your baby is underfed, ensure that you know how to:

  • Breastfeed effectively.
  • Optimize your milk supply.
  • Supplement your baby with milk, if needed.