Change in the three-dimensional shape of the stomach in the developing human fetus.

To reveal the developmental characteristics of the fetal stomach in utero, this study was made on 879 subjects from 20 to 40 weeks' gestation. By applying the system of 'Modeling a three-dimensional shape from a silhouette by detecting symmetry' which we devised, we reconstructed the three-dimensional shape, from the outline of the longitudinally transected fetal stomach, obtained from the real-time ultrasound image. Age-related changes in gastric volume and sphericality (parameters produced by the above mentioned method) were analyzed using piecewise linear regression. The fetal stomach volume increased linearly from 20 to 37 weeks' gestation and decreased thereafter to 40 weeks' gestation, with a critical point at 37 weeks' gestation. The sphericality of the fetal stomach shape was also seen to decrease linearly from 20 weeks' to the critical point at 27 weeks' gestation, thereafter remaining constant regardless of the advance in gestation to term. These findings indicate that at 20-27 weeks' gestation, the stomach is of a fusiform-like shape. From 27 weeks' gestation onwards, greater and lesser curvatures become apparent, clearly identifying the cardiac and pyloric regions. The decrease in stomach size after 37 weeks' gestation is also in good accord with the decrease in amniotic fluid volume. The analytical method presented here can help to understand the pathogenesis of gastrointestinal lesions in the developing fetus.