Growth of a Breastfed Baby

Growth of a breastfed baby
Weight gain is a helpful measurement for determining how well your baby is doing. This is not the only way to know your baby is thriving, but it is a valuable indicator of health in a baby. If your baby is not gaining well, it can be a sign that breastfeeding is not going well. Or it may mean that a health issue is preventing your baby from growing as expected.

There is a wide range of normal weight gain in babies. Many babies who gain weight slowly are perfectly healthy. It is important to look at all the signs of health when evaluating a baby’s growth pattern.

Signs that Your Baby is Gaining Well

  • Your baby is waking up for feedings.
  • Your baby is alert and active during feedings.
  • Your baby is content after a feeding and has alert periods throughout the day.
  • Your baby has enough wet and poopy diapers each day for your baby’s age. See Poops and Pees for more information.
  • Your baby is gaining weight.
  • Your baby is reaching developmental milestones.

For more information see How to Know Your Baby is Getting Enough Milk.

Growth Charts
In 2006 the World Health Organization (WHO) released new growth charts based on the feeding patterns of thousands of exclusively breastfed babies in six different countries (Brazil, Ghana, India, Norway, Oman and USA). In 2010, Dieticians of Canada, the Canadian Pediatric Society and others developed the WHO Growth Charts for Canada. These are the growth charts commonly used by Canadian healthcare providers. These charts contain five line graphs that indicate the expected growth curves for children from the smallest normally growing children (the 3rd percentile) to the largest normally growing children (the 97th percentile). A child who is in the 3rd percentile is smaller than 97 percent of babies the same age. A baby who is in the 97th percentile is smaller than only 3 percent of babies the same age.

It doesn’t matter where your baby is on the growth chart. What is important is that your baby’s growth is relatively consistent on a curve.

Benefits of newborn weight loss
All babies lose weight initially after birth. This normal weight loss may help protect babies from obesity later in life. Two different studies revealed that babies who gained more than 100 g (3.5 oz) in the first week of life were significantly more likely to be overweight later in life. If you are only breastfeeding, your baby will start gaining weight by the second week. Unlike babies who are given formula, exclusively breastfed babies are less likely to gain too much weight in their first week of life.

Impact of C-section vs. vaginal birth
On average, babies born by a cesarean birth lose more weight than babies born vaginally. Exclusively breastfed babies born by a vaginal birth have a median weight loss of 7.1%. Those born by a cesarean birth have a median weight loss of 8.6%. They also lose more weight for a longer period of time (more than 72 hours) than exclusively breastfed babies born vaginally (between 48 and 72 hours). This is perhaps because the medications used in labour (epidurals and narcotics) can remain in the baby’s system for up to a week. This can make your baby sleepy and nursing more difficult in the early days.

Impact of IV fluids in labor
Several studies have found that the larger the volume of IV fluids a mother receives during labour, the more weight her baby loses in the first 24 hours. This is because the IV fluids pass to the baby’s body and increase the baby’s birth weight. In the first 24 hours after birth babies, whose mothers received IV fluids during labour, produce more wet diapers than babies, whose mothers do not receive IV fluids. The extra wet diapers result in an extra weight loss.
Newborn weight
This weight loss is completely unrelated to how much colostrum the baby drinks in the first 24 hours. If you have received IV fluids during labour, it is recommended that you measure your baby’s weight 24 hours after birth. At this time, most of the excess water will have been peed out. This 24-hour weight can be used to measure your baby’s future weight loss more accurately than the inflated birth weight.

Other factors that influence birth weight
Canadian researchers found that the following factors can influence weight loss:

  • Heavier babies lose more weight.
  • Babies born earlier than 40 weeks lose more weight.
  • Baby girls lose more weight than baby boys.

Impact of gestational diabetes on weight gain in the first few days
If you have gestational diabetes, your milk may come in a day or two later than expected. This can lead to greater weight loss in your baby in the first week. You can prepare for this possibility by expressing your colostrum during pregnancy. Bring it with you to the birth and feed it to your baby, if needed.

Prenatal colostrum expression
Most women with low-risk pregnancies can begin hand expression at 37 weeks. Consult your healthcare provider if you have any concerns. This colostrum can be stored in small syringes or small glass jars in your freezer. If your baby loses more weight than normal in the first couple of days, your stored colostrum can be given to your baby by cup or syringe after breastfeeding. The volumes of colostrum in the early days are too small to give with a bottle. See Prenatal Colostrum Expression for more information.

Reasons for concern in the early days
Weight loss of more than 10% is reason for concern. If this is the case, your baby should be examined by a doctor for signs of dehydration. Positioning, latching and breastfeeding management also need to be evaluated, ideally by an International Board Certified Lactation Consultant (IBCLC). Supplementation may be required if there is significant weight loss and/or if breastfeeding is not going well. Dehydration can lead to serious health problems.

In most situations, the reason for excessive weight loss is poor positioning and latching. This can result in your baby not getting enough milk. The second most common cause of excessive weight loss is a delay in milk production. This may be a result of poor latching or other factors. See Positioning and Latching for more information on how to improve milk transfer.

Weight loss - birth to days 3 to 5
It is normal for babies to lose weight in the first few days of life. Babies will begin to gain weight after the milk increases (‘comes in’) between days 3 and 5. If your milk increases on day 3, your baby will begin to gain weight earlier than if your milk comes in on day 5. This is normal. As long as your baby has a good deep latch and is removing milk well with frequent feedings, your colostrum is all your baby needs until your more mature milk comes in.

Remember, that your baby’s lowest weight will be the day before your milk comes in. If your baby is not weighed on the day of her lowest weight, you may not see the initial weight gain that happens when your milk increases.

Weight gain after days 3 to 5
Once your milk supply increases, babies are expected to gain about 20-35 g/day (⅔ oz - 1 1/4 oz/day). Some exclusively breastfed babies will gain considerably more weight. This is in the range of normal.

Back to Birth Weight
Many healthcare providers expect a baby to return to her birth weight by two weeks of age. However, it may take two weeks or more for your baby to regain her birthweight if:

  • you received IV fluids during labour
  • nursing was not going well in the first few days due to poor positioning and latching or delayed milk production.

When nursing is going well, most babies return to birth weight by 5 to 8 days of age. If you have had a difficult start to breastfeeding, your baby may not have gained well during that time. The important thing is to get the support you need to improve breastfeeding. Once your baby is gaining about 28 g/day (1 oz/day) you can rest assured that your baby’s weight is increasing normally.

After the first two weeks
On average, babies gain between 140 g - 245 g/week (5 oz to 8 ¾ oz/week) for the first three months of life. After three months, your baby’s weight gain will slow down. If your baby is on a lower curve on the WHO Growth Chart, your baby will gain at the low end of this range. If your baby is on a higher curve, your baby will gain at the high end of this range. See “Growth Charts” section above.

Slow Weight Gain - a sign of a problem
It is distressing to learn that your baby is not gaining well. You may have suspected this or it may come as a surprise. You may feel guilty or defeated. Contacting a La Leche League Leader for support can be helpful.

Some mothers wonder if their milk is of poor quality, particularly if their babies are not gaining well. This is very unlikely, particularly in Canada. See Low Milk Production, What is in Human Milk.

It is important to evaluate the possible causes for your baby’s slow weight gain.

  • The most common reason for slow weight gain is poor positioning and latching. A poor latch results in poor milk transfer. Your baby is unable to get the milk he needs to grow. This should be considered first. See Positioning and Latching for more information.
  • Your baby may have a tongue tie or tight frenulum. This means the tissue below the tongue is tight and does not allow the tongue to move normally. When a tongue tie is present your baby may have difficulty latching or not be able to latch deeply. And you may have sore nipples. Consult your healthcare provider for an evaluation.

If positioning and latching are good, consider the following:

  • Scheduled feedings, swaddling, rooms that are too warm and pacifiers may reduce your baby’s feeding cues. Not feeding your baby often enough can lead to slow weight gain. See How to Know Your Baby is Getting Enough Milk for more information.
  • Low milk production results in poor growth. This is often caused by a difficult start which results in insufficient milk removal in the early days and weeks. With the support of a La Leche League Leader or International Board Certified Lactation Consultant (IBCLC) milk production can often be increased. Low milk supply can also be caused by breast surgery, insufficient breast tissue, hormonal complications or a retained placenta. If it is not possible to rebuild your milk supply, be encouraged that you can continue to breastfeed your baby while supplementing with donor milk or formula. See Low Milk Production and Establishing Your Milk Supply for more information.
  • There may be other health issues that are making it difficult for your baby to gain weight, like an infection or cardiac issues. Consult your healthcare provider.

Slow Weight Gain - normal for your baby
If positioning and latching are good, there is no anatomical issue and you have sufficient milk production, consider:

  • Your baby may not want to eat more than he is currently eating. Some babies who gain weight slowly are perfectly healthy. They are simply going to be smaller babies. This may be the case if
    ~you have a plentiful milk supply.
    ~your baby is content after feeding.
    ~your baby is healthy and meeting developmental milestones.
    ~your baby is breastfeeding eight to twelve times (or more) a day.
  • Before considering supplementing with formula, try consistently offering your breast to your baby for a period of time, without forcing it. If your milk is available and your baby is refusing it, there is a strong possibility that your baby is a content thriving baby who does not require any more milk.
  • At some point in the first year or two, your baby’s genetics will begin to influence your baby’s weight gain. Big babies are not always born to big and tall parents. And small babies are not always born to parents who are below average in height. At some point in the first year or so of life, your baby’s growth will adjust to align with her genetic expectations.

If you are worried about your baby’s growth, consult your healthcare provider. You may also want to attend an LLLC meeting to talk with other parents about their babies growth patterns.


Mohrbacher, Nancy. (2020). Breastfeeding Answers: A Guide for Helping Families, Second Edition. Nancy Mohrbacher Solutions, Inc.

Updated May 2023