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 IBCLC, 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 growth.

That is contrary to a lot of non-clinical discussion you’ll read out there on the internet 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 (~30ml) 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 babies 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’s 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suggest exclusively breastfed babies be fed 2-10 ml per feeding and they reference the infant stomach size according to outdated studies (1992 and 1920) to reflect intake volume.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.

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?

Turning to other popular breastfeeding education resources for new mothers that discuss infant intake needs and stomach size, you’ll find The Office of Women’s Health in the US, The Le Leche League, WIC programs, IBCLC’s, CLC‘s are also teaching mothers that their newborn’s stomach size is 5-7 ml on day one.

Why the volume difference between formula and breastfeeding newborns despite the same caloric amount? Why are hospitals able to feed an infant 10-30ml 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.”

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:

I continued to search for more resources and I found more recent research in 2013 from Dr. Nils 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 ever 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 easily 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 and brain-threatening low blood sugar (hypoglycemia).

My concern as a long-time NICU nurse and IBCLC has always been why are mothers  taught universally that their exclusively-breastfed newborn baby only needs 5-7 mL of colostrum per feeding when clearly there is no scientific evidence that supports it (and why clinical experts currently feed infants more, based on science that is available)? Gastric emptying is complete in one hour into the small intestine which allows for milk volume to be more than 5-7 ml every 2-3 hours as recommended. Restricting a child’s feeding to 5-7 mL even as often as every one hour will not meet the daily caloric requirement of a newborn and can quickly lead to starvation and hypoglycemia.

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 calorie requirements. 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 when exclusively breastfeeding.

It’s time to ditch the belly models, update our breastfeeding education resources according to the current scientific resources  and practice science based infant feeding practices! Our babies are counting on us to keep them well-fed, meeting their metabolic needs with correct intake volume using the best and current infant feeding practices possible.

See below for additional resources:

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

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.