Abstract
Objectives. To present two- and four-dimensional ultrasound illustrations of fetal defecation and formulate a hypothesis for the determinants of fetal stools color.
Materials and methods. We studied 305 fetal anuses between 14 and 41 weeks of gestation with ultrasound imaging. Fetuses <24 weeks of age underwent macroscopic examination of their stools at the time of genetic amniocentesis. Among 20 amniotic fluid sediments collected, 10 were kept in test tubes exposed to air and light and 10 remained in dark and hermetically sealed test tubes.
Results. At least one expulsion of rectal contents was observed in all cases studied. The collected stools were whitish except in one case, where the sample was greenish. The amniotic fluid sediment remained whitish when kept in a sealed tube, and became greenish when the test tube was open.
Conclusions. Fetal defecation is a physiologic function. Stools are whitish in color. A fetus-dependent biochemical mechanism seems to promote the stool coloring.