In-utero development of the fetal colon and rectum: Sonographic evaluation

Objective: To construct a normal range for the internal diameter of the fetal descending colon and rectum during gestation. Subjects and Methods: This was a prospective, cross-sectional study including 379 healthy pregnant women with normal singleton pregnancies at 19-40 weeks of gestation. Measurements of the fetal descending colon (maximum internal diameter) and the fetal rectum (at the level of the bladder, measuring the anteroposterior diameter), were performed by high-resolution transabdominal sonography. Results: Adequate bowel measurements were obtained in all 379 fetuses. The diameter of the descending colon and rectum plotted as a function of gestational age had a sigmoid curve; the curve estimation was expressed by a cubic regression equation with R² of 0.848 and 0.831, respectively (P < 0.0001). The normal mean and the 95% prediction limits were defined. Conclusion: The present data provide a normal range of fetal bowel (descending colon and rectum) diameters from the early second trimester of pregnancy onwards. They may allow intrauterine assessment of the development of the fetal colon and may serve as reference values in the detection of anomalies of the fetal bowel.