BACKGROUND: An increased frequency of hyperechogenic bowel on ultrasound has 
been reported in fetuses with cystic fibrosis (CF) and trisomy-21. However, the 
diagnostic application of this observation has been hampered by the absence of a 
means of measuring echogenicity.
METHODS: We devised an ultrasonic grading system in which echogenicity was 
quantified by linear gain reduction and comparison with fetal iliac crest. From 
7400 second-trimester ultrasound referrals, 145 patients were identified as 
having a fetus with abnormally echogenic bowel. They were offered genetic 
counselling, parental and (if appropriate) CF carrier testing, and amniocentesis 
for karyotype and CF status if parents were informative. Follow-up was to 4 
months of age.
FINDINGS: Of 40 fetuses with mild increase in bowel sonodensity (grade 1), none 
had CF or aneuploidy. Of 81 patients identified with a moderate increase (grade 
2), 2 had trisomy 21 and 2 had CF. And of 24 pregnancies with a pronounced 
increase (grade 3), 5 had CF and 6 had trisomy-21.
INTERPRETATION: Parental CF carrier testing and amniocentesis to identify 
aneuploidy or fetal CF status has a high positive ascertainment rate in fetuses 
with echogenic bowel grades 2 and 3.