How C-Sections & IV Fluids Affect Weight Loss in Breastfeeding Newborns

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Is your newborn losing too much weight in the hospital? Is it taking baby longer than expected to get back to birth weight? Turns out birth circumstances can affect newborn weight loss. Here’s why you should pay attention to your baby’s 24 hour weight, especially if you had–or plan to have–an induction, epidural or C-section.

Nearly all babies lose weight after birth, regardless of if they are breastfed or formula-fed. This happens because babies are born with some fluids in their systems that are eliminated after birth. It’s very normal.

What They Don't Tell You About Breastfeeding

This is what they don’t tell you in the hospital. Our FREE guide will give you 12 breastfeeding secrets that will help you avoid common problems down the road. 

During these early days of life, baby’s weight gain (and diaper output) gives us a sense of how well breastfed babies are feeding. After all, we can’t look into the breast to see how much milk baby drank. The amount of milk you can pump doesn’t give us an accurate picture of how much baby is drinking, either. So we monitor breastfeeding by paying close attention to baby’s birth weight and making sure they don’t lose more weight than expected after birth. 

But if you’re planning on having a C-section, induction, or epidural, you might want to also pay attention to baby’s 24 hour weight. Here’s Why:

How C-sections and IV fluids affect weight loss in breastfeeding newborns


Research has shown that IV fluids given during labor or before a planned C-section can artificially inflate a baby’s birth weight (source). IV fluids are given to prevent dangerous drops in blood pressure during C-sections and epidurals, and they’re used to dilute some medications needed to induce labor. When birthing parents receive high IV fluid loads, their babies tend to hold on to some of that fluid. As a result, these babies are born weighing more than they otherwise would have.

After birth, these babies tend to urinate more in the first 24 hours of life in order to regulate and balance their fluid levels. In other words, they expel extra fluids on top of what’s normal. And this gives the appearance of excessive weight loss.

Researchers have found that in these situations, a baby’s weight at 24 hours old—after they’ve been able to expel the extra fluids they were holding onto—is likely more representative of what that baby would have otherwise weighed at birth (source). 

If your goal is to breastfeed, here’s why knowing about this weight loss phenomenon matters:

Maternal IV fluids can make breastfed babies appear to lose extra weight in the first 24 hours after birth


It is expected for babies to lose some weight after birth. But when babies lose more than 7% of their birth weight, healthcare professionals start to get nervous. Doctors will assume (often correctly) that baby isn’t feeding well and will suggest supplementing with formula. 

In normal circumstances, excessive weight loss IS a sign that baby may not be feeding well, and supplementing with formula is actually warranted. There is NOTHING wrong with necessary supplementation. 

But unnecessary supplementation—especially soon after birth—can have a negative impact on breastfeeding and milk supply (source, source, source).

This happens for a number of reasons. For example, babies can quickly develop a bottle preference: Bottles release milk easier and faster and require the use of fewer and different facial muscles (source). When baby receives a bottle, your body doesn’t get the signal it needs to keep producing milk (source). All of this can cause a baby to reject the breast and can cause parents to quit breastfeeding early. 

Supplementing to prevent excessive newborn weight loss
Expressed milk (or formula, if needed) can be fed from a cup, spoon, or syringe if you need to supplement in the hospital.

The good news is, there is much we can to do prevent these things from happening if baby needs supplementation, such as pace feeding bottles, supplementing with your own expressed milk, and expressing milk to protect your supply.

READ MORE: Breastfeeding After a C-Section or Induction: How To Set Yourself Up For Success


About 1 in 3 babies in the U.S. is born via C-section (source). About 71% of birthing parents receive epidural anesthesia during birth (source). And labor is induced in about 30% of births in the US (source). 

So it is perhaps not surprising that in the US, nearly 20% of babies are supplemented with formula before 2 days old (source). We would not usually expect to see excessive weight loss this early, since its actually normal for a breastfeeding parent’s milk to come in 3-4 days after birth (source).

Birth circumstances can impact newborn weight loss
Birth circumstances can have a surprisingly significant impact on breastfeeding later.


The purpose of this post and my story above is NOT to say “you shouldn’t supplement” or “don’t listen to your pediatrician.” Supplementation is sometimes necessary, and you should always follow your healthcare provider’s advice or seek a second opinion from another qualified provider. 

Instead, the purpose of this post is to let you know that sometimes, numbers don’t tell the full story. 

If your baby is one of the 14-24% of babies who are not back to birth weight by the usual 2 weeks old (source), it might not be because of a breastfeeding problem. And if it’s not, you’ll want to avoid “solutions” that can interfere with breastfeeding, like unnecessary supplementation.

That said, weight loss and slow weight gain are often red flags for breastfeeding issues. So the safest course of action is to meet with a qualified lactation consultant to rule out breastfeeding problems any time baby isn’t back to birth weight by 2 weeks old or isn’t gaining weight at the expected rate. 


My second baby was born via C-section after an unsuccessful VBAC attempt and 6 liters of IV fluids. She weighed 9lb 5oz at birth. She weighed 8lb 12oz at 24 hours old and 8lb 6oz at discharge 3 days after she was born. 

If you compare her discharge weight (8lb 6oz) to her birth weight (9lb 5oz), the drop in weight (10%) would make any reasonable pediatrician nervous. But if you compare her 24 hour weight (8lb 12oz) to her discharge weight (8lb 6oz), the drop in weight is less alarming (4%). 

Graph of newborn weight loss and weight gain

Initially, the hospital pediatrician was concerned my daughter wasn’t feeding well based on how much she weighed at three days old compared to her birth weight. He wanted us to supplement with formula, but we asked him to reconsider his recommendation in light of my birth (C-section + high IV fluid load) and our daughter’s 24 hour weight.

He agreed and instead instructed us to check in with our regular pediatrician the day after discharge, which we promptly did. Our regular pediatrician was not concerned about my daughter’s weight loss in light of my IV fluid load at birth.

My daughter went on to gain a whopping 8 ounces over the next three days (normal expected weight gain would be closer to 1 ounce a day). Turns out she was breastfeeding just fine. She went on to return to birth weight by 2 weeks old and followed her growth curve well.

Again, this just goes to show that sometimes weight loss numbers don’t tell the full story. If you had a C-section, an epidural, or a lot of IV fluids during labor, talk with your child’s pediatrician about how this might affect his or her assessment of baby’s weight gain.

What They Don't Tell You About Breastfeeding

This is what they don’t tell you in the hospital. Our FREE guide will give you 12 breastfeeding secrets that will help you avoid common problems down the road. 

If you enjoyed this post, be sure to check out our digital library of helpful resources that quickly teach how to avoid common breastfeeding problems and give you the peace of mind and confidence you need to meet your breastfeeding goals.

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