To elucidate processes involved in the developing fetal stomach in utero, we examined chronological changes in maximum longitudinal and anteroposterior gastric dimensions in 618 fetuses from 16 to 41 weeks of gestation, using real-time ultrasound. Three statistically critical points were evident at 26-27, 32-33, and 36-37 weeks of gestation. Both dimensions increased from 16-17 to 26-27 weeks, remained fairly constant between 26-27 and 32-33 weeks, increased again from 32-33 to 36-37 weeks, and then decreased from 36-37 weeks onwards. These findings suggest that there are four different phases underlying the development of gastric function in the human fetus, corresponding to the time-periods divided by the three critical points of gestational age.