Baby's Weight Gain in the First Year

by Sabrina Granniss, IBCLC May 25, 2022

Baby’s weight gain and making enough milk are two of the top concerns new parents have. What does weight gain look like during the first days and weeks of your baby’s life? What about after that? There are some guidelines to keep in mind when looking at how your baby measures up for weight gain during the first year. Many factors influence your baby’s weight loss immediately after birth as well as their growth during the first couple of weeks and beyond.

Overview of your baby’s growth(3)

Babies lose an average of 5 - 7% of their birth weight in the first few days after birth(2)
Losing up to 10% of their birth weight is considered acceptable
A Baby’s weight at 24 hours old may be a more accurate representation of true birth weight
Babies lose the most weight in the first 2 days after birth(2)
Your baby should regain their birth weight by the time they are 2 weeks old
During the first 3 months, your baby will gain about 1 ounce per day
By 4 months old, your baby will double their birth weight
From ages 6 - 12 months old, your baby will gain about 3 - 5 ounces per week
Your baby will triple their birth weight by about 1 year old
Boys gain weight faster than girls
Babies grow about 10 inches in length during the first year of life(4)

Growth charts

The United States began using growth charts in 1977. It can be one tool for measuring the growth of your baby. Growth charts are not reflective of your baby. The World Health Organization growth charts show patterns of growth that are the standards for how a baby should grow. They were created by looking at the pattern of growth of babies who predominantly breastfed for at least four months and were still breastfeeding at twelve months of age.(1) Babies' differences need to be taken into account when determining appropriate and acceptable weight gain. Your baby’s length and head circumference should be considered as part of looking at their growth in addition to weight.

How to Read a Growth Chart

Percentile - this shows a measurement of your child’s weight compared to other children the same age
Z-score - the standard deviation above or below the mean. It tells you where your baby’s score is on the curve. For example, a z-score of zero means your baby’s weight is exactly average or 50%. A score of +3 means your baby is above the average and -3 is below the average
Growth curve - It is important to not look at just the numbers alone. Remember, your baby is unique and an individual. They should follow their curve, meaning if they are in the 30th percentile, they should continue to chart at the 30th percentile. Sure, it can be helpful to know what percentage your baby falls into, but it shouldn’t be the only consideration. If your baby is not following their curve or is dropping percentiles, this can be cause for concern and you should meet with your IBCLC (International Board Certified Lactation Consultant) to figure out why and how to help your baby gain weight.

Signs your baby is gaining weight

Between visits to your care provider where your baby gets weighed, you can gauge how well your baby is doing by knowing what to look for.

Your baby looks bigger - as they grow, you see them look more rounded in their cheeks and legs and other areas of their body are filling out
They have plenty of wet diapers per day - your baby should have one wet diaper for each day they are old, until your milk transitions from colostrum to more volume, and by day 5, your baby should have at least 6-8 or more wet diapers. A wet diaper means it is full, not just lightly wet. To know what this looks and feels like, pour 3 Tablespoons of water on a clean dry diaper for reference. If you are not seeing enough pee diapers or there are orange-colored crystals in your baby’s diaper, this is a sign of dehydration and you should call your pediatrician right away.
Poop diapers - after day 4, your baby should have 3-4 or more poop diapers per day. The amount of poop should be at least the size of a quarter. It should be soft yet have substance rather than be liquidy.
Your baby seems relaxed and content after nursing
Your breasts may feel more full before feeding and less full after feeding
Your baby has a rhythm of nursing, sleeping, and some alert time and is mostly happy and content
Your baby rouses to feed every 2-3 hours on their own
Your baby detaches themself when they are done nursing and seems satisfied
Your baby takes up more space in the car seat or bed
They are growing out of their clothes

Keeping on track

Follow your baby’s cues for feeding - expect to breastfeed every 1.5-3 hours around the clock
Middle of the night nursing is important for you and your baby. Prolactin levels are highest during the night and the removal of milk during this time has a big influence on overall milk production. Babies get around 30% of their calories during the middle of the night feedings. It is normal for babies to wake during the night even well past one year old.
During a growth spurt, offer your milk more often, still following your baby’s cues. Growth spurts are common at 7-10 days, 2-4 weeks, 6-8 weeks, 3 months, 4 months, 6 months, and 9 months old.(5)
Always give breast milk before solid foods after the introduction of solids sometime around 6 months of age. Solid foods are complementary to breast milk and should not be given first or in place of breast milk.
Spend time skin-to-skin with your baby as much as possible while breastfeeding is being established and continue lots of contact with your baby as they grow by babywearing in a sling you can nurse in, taking baths together, learning infant massage, and continuing time skin-to-skin.

What can interfere with weight gain?

Medications taken during labor - some medications can make your baby sleepy or disorganized and not able to express their feeding reflexes as well.
intravenous fluids given during labor can result in your baby having more fluids on board and so their weight loss may be more significant as those fluids leave their body
Cesarean section birth - average weight loss is slightly higher for babies born by cesarean section than vaginal births.(6)
Jaundice(7) - your baby might be more sleepy and hard to rouse for feeding.
Pacifier use - can lead to missed feeding cues. Babies who nurse for comfort as well as for food tend to gain appropriate weight compared to babies who use a pacifier regularly.
Premature birth - babies born prematurely have more hurdles to overcome and may gain weight more slowly at first.
Swaddling or other sleepsuits/sacks - these interfere with the natural sleep patterns your baby has. It dampens their reactions and scrambles their intrinsic blueprint for wakefulness patterns. They do encourage longer sleep, but babies are hardwired to wake during the night for food. Babies' natural habitat is in close contact with their lactating parents.

What to do if baby has lost weight

Be in close communication with your baby’s pediatrician and your IBCLC
hand express or pump and give the milk to your baby for more calories and to protect your milk supply
Stay skin-to-skin with your baby and nurse as much as they are willing
Do breast compressions during nursing
Offer to feed your baby more frequently during the day paying close attention to their cues
Include lactogenic foods and hydrating foods in your diet to support and boost your milk supply
Use high-quality lactation supplements to support milk production and encourage milk flow. Supplements are a helpful tool but do not take the place of getting to the root of your milk supply or baby’s weight gain issues

Each baby has a unique set of circumstances to consider when looking at its overall growth. Growth charts are there to help you determine if your baby is growing well. Seeing your baby grow and thrive is very rewarding as a parent and their growth during the first year of life is extraordinary. They will go from a newborn relying completely on you for everything to becoming a walking, laughing and more independent, wonderful toddler.