Belly models as teaching tools: what is their utility?

Marble/ball models are often used to represent newborn stomach capacity; however, their accuracy has not been determined. The objective of this review was to analyze data on newborn stomach capacity and determine whether marble/ball models serve as accurate representations. A literature search yielded limited data, most emanating from the early 1900s. Data suggest that anatomic capacity of the newborn stomach varies with the birth weight of the infant. Physiologic capacity bears no relation to anatomic capacity of the newborn stomach but is a measure of the ability of the mother to produce milk and the newborn to ingest milk. Given the wide range of feeding volumes on days 1 and 3 and the reported 8-fold increase in average feeding volume during the same time period, it is best to acknowledge that feeding volumes like anatomic stomach capacity vary widely and do not lend well to visual representation by marble/ball models.