The Newborn Stomach Size Myth: It is NOT 5-7 mL

Written by Jody Segrave-Daly, RN, IBCLC

As a veteran NICU, nursery nurse and lactation consultant, I have taken care of and fed thousands of babies over the years. When working in the special care nursery, babies were always fed according to their weight and cumulative losses, to determine their caloric requirements for intake amounts and optimal nourishment. For example, term babies who are admitted to the NICU from complications of not receiving enough colostrum are immediately fed based on their weight, usually about 60-80 ml/kg/day (typically 15-30 ml) every 2-3 hours. When allowed to feed on demand, newborns will typically take  increased volumes eagerly and demonstrate feeding satisfaction and comfort.  Why do some babies tolerate fasting before the onset of copious milk production and other babies do not? 


This is contrary to a lot of non-clinical discussion you’ll read out there on the internet in a plethora of mommy groups about an infant’s intake needs, which suggest it’s mostly based on stomach size. So what’s fact and what’s fiction?


Calories and Feeding Amounts for Breast Milk, Formula, and Colostrum

What science tells us is that mature breast milk averages around 20 calories per ounce (~30 mL) and formula contains approximately 20 calories per ounce as well. Thus their per-milliliter (mL) calorie count is on average the same. Colostrum, a key substance that imparts passive maternal immunity to a newborn in the first few days of life if a mother breastfeeds, is lower in fat and carbohydrates than those two, and comes in around 17 calories per ounce (~30ml) (Guthrie 1989).

#2 Why Fed is Best- CaloriesColostrum(1)

With that knowledge in mind, current hospital feeding protocols for formula-fed newborns range from feeding 10-30 ml for newborns less than 6 pounds’ every 2-3 hours and feeding newborns over 6 pounds 10-30 ml every 3 hours on the first day of life.

But according to the newly updated Academy of Breastfeeding Medicine Supplementation Protocol, they suggest exclusively breastfed babies be fed 2-10 ml per feeding and they reference the infant stomach size according to outdated studies (1992 and 1920) to reflect intake volume. As you can see, that’s substantially less for a feeding than our current hospital clinical protocols state. They also say there is no definitive research available and the amount of supplement given should reflect the normal amounts of colostrum available, the size of the infant’s stomach and the age and size of the infant. Intake on day 2, post birth is generally higher than day 1 in relation to infant’s caloric demand. Based on the limited research available, suggested breast milk intakes for healthy, term infants their feedings should be based on satisfaction cues despite their guidelines. Unfortunately, this information contributes to additional confusion that already exists for parents.

Fortunately, what they do say is research is necessary to establish evidence-based guidelines on appropriate supplementation volumes for specific conditions and whether this varies for colostrum versus infant formula. Specific questions include the following:

Should the volume be independent of infant weight or a per kilogram volume? Should supplementation make up for cumulative losses, like we do in the nursery and NICU?

Many popular breastfeeding education resources for new mothers, also refer to inaccurate information by teaching mothers the stomach size is 5-7 ml on day one. This picture is from a mother who delivered this week in a Baby Friendly Hospital. Imagine her confusion when her baby required additional amounts of supplementation to prevent complications and no one could explain to her why her baby could comfortably tolerate more milk than what she was taught in this resource booklet.

A breastfeeding booklet for mothers in a BFHI hospital.

Why the volume difference between formula and breastfeeding newborns despite the same caloric amount? Why are hospitals able to feed an infant 10 – 30 mL on day one if their stomach size is allegedly at most, 7ml? And where did the current idea of newborn stomach size (and with it, an “optimal” calorie amount) originate from?  I decided to find out.

The Myth of the Newborn Stomach Size: Where Did it Come From?

I started my research with my non-clinical hat on and turned to Google, since this is where my patients typically go first. When I did a Google search for newborn stomach sizes there were over 868 thousand links!  I was led to a plethora of visual images depicting newborn stomach size. Some of the most popular images were the belly ball models that lactation consultants wear on their lanyards so they can visually educate new mothers how big their newborn’s stomach size “is.”

I was in disbelief knowing our most trusted breastfeeding experts were wearing and using, proudly I might say, very inaccurate information. I quickly began to understand that ‘belly bead’ models are lucrative merchandise to sell!  

Clinical hat back on, I dug into the science behind these belly balls. In the 2008 Journal of Human Lactation I found a published article that revealed a completely different utility for belly ball models.

Marble/ball models are often used to represent newborn stomach capacity; however, their accuracy has not been determined:

“Measurement of infant stomach capacity has been attempted for over 100 years. Exact volumes cannot be standardized, but data suggest that anatomic stomach capacity and physiologic stomach capacity vary widely.” In addition, “It is important to note that because a wide range of feeding volumes on day 1 (1.1-20.4 mL) and day 3 (13.1-103.3 mL) has been reported, and the reasons for these variances are unclear, it may be best to simply acknowledge that feeding volumes vary widely and like stomach capacity, do not lend well to visual representation given our current knowledge.”

Despite that qualification, new moms are inundated with images where there are a series of bottles filled with milk depicting the size of an infant stomach according to each day after birth, sometimes compared with fruit or different sized marbles and balls. A mother sent this picture to us which was in her hospital room after the birth of her baby. She also received inaccurate information and thought her formula fed baby only needed 5 ml at each feeding. 

I continued to search for more resources and I found more recent research in 2013 from  Nils J. Bergman who published this study, which says:

“There is insufficient evidence on optimal neonatal feeding intervals, with a wide range of practices. The stomach capacity could determine feeding frequency. A literature search was conducted for studies reporting volumes or dimensions of stomach capacity before or after birth. Six articles were found, suggesting a stomach capacity of 20 ml at birth.”

Stomachsize1.pptx (1)

I also found this research  depicting infant stomach size.StomachSize

According to Dr. Bergman, “There is reasonable consensus on the amount of milk that human term newborn infants need per day, figures given vary from 150 to 160 mL/kg/day.” This means that an average 3 kg or 6.6 lb newborn requires 450-480 mL or 16 ounces of milk a day.  At 66 Calories/dL, this would roughly be 100-106 Cal/kg/day, which is the published daily caloric requirement for a newborn.  This total volume can be given in smaller volumes more frequently or larger volumes less frequently, 2 ounces every 3 hours or 1.3 ounces every 2 hours.

His article poses the hypothesis that the feeding interval should be 20 mL every 1 hour assuming that the stomach empties only once every hour. However, the real-life clinical application of this feeding interval would quickly lead to maternal and newborn exhaustion from lack of sleep and increased risk of postnatal depression, breastfeeding cessation and even suffocation from a mother falling asleep with her newborn during breastfeeding. In addition, his feeding interval does not take into account that the stomach actually empties during feeding and therefore the feeding capacity of a newborn is higher than 20 mL. Feeding capacity and satisfaction actually depend on the release of the hormones CCK and amylin, which slow down stomach emptying and signals the brain to stop accepting food. The clinical experience of health professionals has shown that even one-day old newborns are able to comfortably tolerate 15-30 mLs per feeding. 30-60 mL every 2-3 hours would in fact meet a newborn’s full daily caloric requirement and therefore prevent starvation-related complications.

Here is another resource in the Pediatric Surgery Journal describing the newborn stomach anatomy, including the size of 30 ml at birth:

My concern as a long-time NICU nurse and IBCLC has always been why are mothers taught  that their exclusively breastfed newborn baby’s stomach capacity is only 5-7 mL on day one.  Gastric emptying is a continuous movement into the small intestine which allows for milk volume to be more than 5-7 ml every 2-3 hours as recommended.  The stomach is a muscular organ and its biological function is to hold food and fluids before entering the duodenum. Yes, some exclusively breastfed babies are in a state of fasting after birth from limited amounts of colostrum some mothers make. But some of these babies will develop complications from insufficient intake because parents are not taught how to identify the signs in order to prevent them.

But, as professionals we need to update our educational resources and identify the babies who may need timely supplementation before the onset of copious milk production. For mothers who desire to exclusively breastfed, donor milk must be made available for them to use if supplementation is needed. In order for babies to receive the full benefits of breastfeeding, they need to be safely fed at every feeding.

So how often should exclusively breastfed babies eat?

There is no single right answer to this question because each baby has a different weight and unique caloric requirement. By just weight alone, a 6.6 pound baby has an average size stomach of 20 mL on day 1 and would require 40 mL or 1.3 oz  of breast milk or formula every 2 hours to meet their basic metabolic needs or 60 mL every 3 hours. But babies should also be fed by infant cue to satisfaction. In other words, if your baby is crying and crying after breastfeeding, an immediate medical exam is necessary to be sure the baby is not suffering from insufficient intake at breast while exclusively breastfeeding. If medical evaluation is not immediately available, especially before milk has come in and/or while baby is losing weight, supplementation may be needed before medical evaluation is available in order to prevent serious complications of insufficient feeding.

As you can see, It’s time to ditch the belly models and update our breastfeeding education resources .  Our babies are counting on us to keep them well-fed, meeting their metabolic needs with sufficient milk and using the best and most current infant feeding practices possible.

See below for additional resources:

Pediatric Anatomy Surgery Journal

Normal third trimester fetal anatomy -ultrasound videos: the abdomen:

Guthrie, Helen Andrews. Introductory Nutrition. St. Louis : Times Mirror/Mosby College Pub., 1989

Breastfeeding confidence and measurement of milk intake

The American Academy of Pediatrics’ Breastfeeding Guidelines

Helpful guide to safe infant feeding amounts from the American Academy of Pediatrics.

Helpful overview of infant feeding for the first month of life, from the American Academy of Pediatrics.

Normal Human Lactation; closing the gap


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