Birth educators and medical professionals often use a marble to illustrate the size of a newborn’s stomach, a tiny orb that holds about 5 to 7 milliliters of liquid.
Human Lactation points out that there aren’t many solid studies on the size of the infant stomach, and some of the ones that do exist come to different conclusions.
The question of stomach size at birth isn’t settled, and that may be in part because there is no one answer. Just as babies come in a variety of sizes, their stomachs may too. What’s more, size isn’t everything. Drinking ability, the stretchiness of the stomach and the speed at which food gets digested are all part of the equation, and those physiological skills may take a few days, or longer, to get sorted out.
Because we don’t really know how big any particular newborn’s stomach is, the best approach to feeding frequency comes from watching the baby’s behavior.