Baby Tummy Size: According to Science
You’ve probably seen the below chart from Ontario Public Health shared at your Hospital or by your midwife/birth attendant.
www.beststart.org
Or maybe you are just coveting my “belly bead” earrings…
In any case, the accepted and widely shared infographic asserts that your baby’s stomach is the size of a cherry/marble at birth and grows to the size of a walnut/ping pong ball by day 3.
Why does it matter?
Because your first milk, colostrum, is very small in amount. New parents worry that they “don’t have enough milk” for their new baby and sometimes resort to formula supplementation when it isn’t medically indicated.
That said, modern birth interventions such as epidurals, c-sections, inductions etc. have been shown to impact breastfeeding ability of the newborn. In addition, fewer parents are familiar with breastfeeding before they have a child since (at least in North America) public breastfeeding isn’t prevalent and low breastfeeding rates mean less parents have seen others breastfeed at all. Breastfeeding rates were even lower (like, only 25% of Canadians started breastfeeding at all) in the 1960s, so newly-minted grandparents these days are unlikely to have personal experience with breastfeeding.
But, is it true?
Um… maybe?
The stomach is a stretchy organ. It can expand to accommodate larger volumes, in addition to actually growing in size as a child grows. As a result, the idea that there is a stomach “size” is actually one of two things:
Anatomical size: as big as the tummy can stretch
Physiologic size: as big as the tummy should stretch
The research regarding the “2-7ml” that you see everywhere (including in the document above) is based on a 1920 study (Ref 1). Obviously, we have better research tools now.
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Recent ultrasound studies of fetuses in utero vary widely in result.
An Egyptian study last year concluded that a 40-week old fetus had a stomach volume of 9 - 24 ml (Ref 4).
A 2018 study had a mean stomach volume of 6 cubic centimetres, which is roughly equal to 6 ml (Ref 3).
In 2005 the Journal of Perinatal Medicine established the average volume of a term baby’s stomach as ~15ml (Ref 5).
And the Pediatric Surgery Journal claims a newborn’s stomach size is 30ml at the time of birth, but didn’t cite where they got this (Ref 6).
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Another study in 1984 determined that average feeding volumes in the first few days were close to the “belly bead” model after all (Ref 2)
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A recent study confirmed that higher-volume feeds were associated with higher chances of feeding intolerance. And consensus is growing after multiple studies correlate that increased feeding volumes in the first days of life are associated with higher risks of obesity in adulthood.
In conclusion…
The “belly beads” are a teaching tool, imperfect as they are, and should be more appropriately referred to as “serving size” rather than “tummy size”.
Although your baby’s tum-tum is bigger than a marble (the smaller bead) at birth, their intake is likely to be just a few ml at a time, 8-12 times a day. Their belly will rapidly grow over the first few days, which matches with mature milk “coming in” in higher volume. Frequent feeding of colostrum in the first couple of days encourages mature milk to come in faster and in higher volume.
In summary: you are enough, your colostrum is enough, and the more you can feed your baby (or hand express!) in the first couple days, the better off parent and baby will be on their breastfeeding journey.
One more thing - the above info is a generality, and is applicable only to full-term healthy infants. Listen to your doctor if they give you an alternate feeding schedule to what I mention here. If you want a second opinion or to understand your doctor’s orders, find a local IBCLC to chat with!
References:
Scammon R, Doyle L. Observations on the capacity of the stomach in
the first ten days of postnatal life. Am J Dis Child. 1920;20:516-538
Saint L, Smith MM, Hartmann P. The yield and nutrient content of col-
sotrum and milk of women from giving birth to 1 month post-partum.
Br J Nutr. 1984;52:87-95
Ennen, Christopher S. et al. Fetal gastic size: linear and volume measurements and temporal changes. American Journal of Obstetrics & Gynecology, Volume 218, Issue 1, S256 - S257
Mousa, Waleed Abd Elfattah et al. Standardization of Reference Values for Fetal Gastric Size in Normal Gestation. Eg J of Hosp Med, Volume 90, Issue 2, 2874-2888
Kepkep, K., Tuncay, Y.A., Göynümer, G., & Yetim, G. (2005). Nomogram of the fetal gastric size development in normal pregnancy. Journal of Perinatal Medicine.
Lander A, Newman J. Paediatric Anatomy. Surgery Journal (UK). 2013: 101-105
