Correlation of ultrasonic images of fetal intestine with gestational age and fetal maturity.

In 276 scans of 81 gravid patients, changes in the ultrasonic images of the fetal intestine, particularly the colon, are described at advancing stages of gestation. These changes appear to be related to an increase of the meconium content of the intestine and to its gradual displacement to the colon by a progressively more efficient peristalsis. A grading system of four stages was devised. In stage 1, the intestine has a uniform gray appearance. In stage 2, the colon can be identified by small echo-free areas close to the kidneys and the bladder. In stage 3, these areas become larger and delineate large segments of the colon. The small bowel can also be seen, represented by clusters of numerous transonic areas that continuously change their shape. The colon becomes redundant in stage 4 and the haustra appear. The echo-free areas of the small bowel are larger and show a very active peristalsis.