Ultrasound assessment of fetal intestinal development in the evaluation of gestational age.

A prospective ultrasound study was conducted in 289 uncomplicated pregnancies with gestational ages ranging from 16-40 weeks. Biometric measurements obtained included biparietal diameter (BPD), head and abdominal circumferences, measurements of long bones, and maximal transverse colon diameter. The pattern of small intestinal peristalsis, presence of colonic haustra, and progressive changes in the colon's intraluminal echogenicity were also evaluated. A high degree of correlation was found between gestational age and transverse colon diameter (in millimeters) (R2 = 0.859; P less than .0001), increasing colonic intraluminal echogenicity (R2 = 0.741; P less than .0001), and the appearance and progressive increase in small intestinal peristalsis (R2 = 0.726; P less than .0001). Colonic haustra were visualized in 87.5% after 30 weeks (specificity 100%, sensitivity 77.4%). A high degree of correlation with gestational age was also found if echogenicity and peristalsis were combined (R2 = 0.873; P less than .0001), and proved superior to that found with measurement of BPD (R2 = 0.655; P less than .0001) or femur length (R2 = 0.805; P less than .0001) after 28 weeks. Observations of progressive changes in small intestinal peristalsis and colonic intraluminal echogenicity, together with the development of colonic haustra and progressive increase in transverse colon diameter, allow one to estimate gestational age independent of standard biometry. This approach has particular utility in the third trimester, when sonographic estimation of gestational age is least accurate.