Updated Feb 03, 2024

As a new parent, it’s scary to see your child fall behind on milestones, so it’s important to know why isn't my baby gaining weight.”


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If you’re concerned your baby isn’t gaining weight at an average rate, you’re not alone. It’s normal to be concerned if your baby isn’t gaining weight as quickly as projected, and that’s when it’s time to consult your doctor. Every infant is different, and you’ll have to consider any other health issues you both experienced during labor and delivery. You may also see a clear difference between the weight gain of babies who are breastfed compared to formula-fed. On average, you should be concerned about your baby’s weight if they are gaining weight very slowly or inconsistently. That’s when it’s good to know what to do when your baby isn’t gaining weight! 

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What’s a Normal Growth Pattern for Babies?

Typically, a newborn will lose up to 10% of their birth weight during the first week. By week two, they should regain the weight. Then a breastfed baby will gain about one ounce per day over the next few months.

Babies who breastfeed actually gain less weight over their first year than babies who are fed formula. That’s not to say breastfed babies don’t gain enough weight! They absolutely do. However, breastfed babies are more in control of how much they eat. Formula-fed babies gradually lose their self-regulation and may begin to take whatever is in the bottle rather than stopping when they’re ready. This is why intake monitoring is important. You wouldn’t want to overfeed your infant either, after all.

As far as what to do when your baby isn’t gaining weight, start by determining if they are in the proper percentile for their weight. Your healthcare provider will likely only be concerned if they fall below the third percentile for weight or weigh below 20 percent for their “ideal weight.”

Here are a few tips for what to do when your baby isn’t gaining weight.

Steps to Take If Your Baby Isn’t Gaining Weight

Talk to a Doctor 

First and foremost, contact your child’s healthcare provider immediately! There are many reasons behind why your baby isn’t gaining weight, and only a doctor can properly diagnose them. From there, here are a few suggestions your doctor may have to help your little one get back on track.

Check your Infant’s Latch

If you are breastfeeding, it’s common to experience latching problems. Breastfed babies who have trouble latching may not be getting enough milk. Consider speaking with a lactation consultant if you think this could be a problem for you.

Formula Measurements 

Failure to thrive can result if a parent or caregiver is not measuring or mixing the formula correctly. This results in less calories and, therefore, less weight gain. Unfortunately, this can be common in situations where parents cannot afford enough food.

Keep Them Awake 

Is your baby sleepy during feeding sessions? They may not be gaining enough weight because they frequently fall asleep instead of eating as much as they should. If your breastfed baby isn’t gaining weight, keep their eyes open and actively breastfeed for about 20 minutes. This way, it can be clearer that they’re getting enough nutrients.

Address your Breast Milk Supply 

If you struggle with a low milk supply, your baby may not be getting enough to eat. Try breastfeeding more often, pumping in between feedings or even supplementing with formula to correct the problem. Remember, fed is best and there is nothing wrong with needing help with breastfeeding!

Test for Medical Conditions 

Although much less likely, your child could have a medical condition. This is probably the last resort when your baby is experiencing slow weight gain. Certain medical conditions, infections or metabolic disorders may cause your infant to process calories faster or differently. If your doctor suspects something, they may want to text for different health issues.

Before you make the decision to stop breastfeeding based on your baby’s weight gain, talk to your doctor! It’s good to be concerned and research your options about what to do when your baby isn’t gaining weight, but don’t jump to conclusions. Your doctor will help you find a solution so that your peanut is happy and healthy!

What experiences have you had? What did you do when your baby wasn’t gaining weight?

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Holly Wade

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