Is fetal hyperechoic bowel on second-trimester sonogram an indication for amniocentesis?

To determine the clinical significance of hyperechoic bowel seen sonographically in second-trimester fetuses.

Fifty fetuses (0.6%) with echogenic bowel were identified sonographically from a population of 8680 consecutive second-trimester fetuses over 21 months. The fetal bowel was considered hyperechoic if its echogenicity was similar to that of surrounding bone. Follow-up was obtained through medical record review.

Twenty-nine of 50 fetuses (58%) were normal; eight (16%) were aneuploid, including six Down syndrome, one trisomy 13, and one Turner syndrome. All eight fetuses with aneuploidy had sonographic anomalies in addition to the echogenic bowel. Eight of 50 fetuses (16%) were growth-retarded, and five others (10%) had normal karyotypes but are still undelivered. Among the eight growth-retarded fetuses, there were five intrauterine or neonatal deaths, one elective abortion, and two survivors. In addition, the six fetuses with Down syndrome and echogenic bowel represented 12.5% of all second-trimester Down syndrome fetuses karyotyped in our laboratory during the study period. Combining results from the present study (six Down syndrome fetuses) with three studies from the literature (21 additional Down syndrome fetuses), a total of 27 fetuses with echogenic bowel and Down syndrome were identified, 11 (40.7%) of whom had no other sonographic findings. We calculate that if 1,000,000 second-trimester fetuses were scanned, 5105 would have hyperechoic bowel as the only finding, of whom 71 would have Down syndrome and 5034 would not. The risk of Down syndrome in fetuses with isolated hyperechoic bowel is, therefore, 71 in 5105 or 1.4%.

The finding of isolated hyperechoic bowel in the second trimester should prompt genetic counseling and consideration of karyotypic analysis.