• cystic fibrosis
• echogenic bowel
• ultrasonography

Cystic fibrosis (CF) is the commonest severe autosomal recessive disease that affects children in white populations, with an incidence varying from 1/2500 to 1/5000 (carrier rate 1/25 to 1/35).¹ The disease, which is characterised by chronic pulmonary obstruction and infections, and by digestive disorders such as pancreatic insufficiency, is caused by mutations in a gene which encodes a protein called CFTR (cystic fibrosis transmembrane conductance regulator).

The cloning of the CFTR gene in 1989^2–4 and the identification of more than 1000 mutations,⁵ with geographical and ethnic variations, have enabled prenatal testing for CF by direct detection of mutations. Initially, prenatal testing was only offered to families in which there was a previous history of CF. More recently, the medical assessment of pregnancy performed in some countries has allowed, through systematic ultrasound examinations, the prenatal diagnosis of bowel echogenicity, an abnormality suggestive of CF. The fetus can therefore become the proband in this disease.

Fetal echogenic bowel, defined as bowel with sonographic density greater than that of the surrounding bone, is diagnosed in 0.2-1.8% of fetuses during routine ultrasound examination in the second trimester of pregnancy.^6–10 This intestinal echogenicity was initially described as a normal variant, which usually disappeared at 20 weeks of gestation.^11,12 More recently, it has also been associated with fetal abnormalities, such as chromosomal abnormalities,^{6,8,10,13–17} congenital infections,^18–20 intestinal obstruction,^20–22 and CF. In this latter case, it is probably the result of the malfunctioning of the CFTR protein leading to the dehydration of mucus secretions, which become viscous, obstruct the bowel lumen, and cause meconium ileus.²³ The risk for CF in fetuses with echogenic bowel has been extensively studied^{6,9,10,13,16,20,21,24–30} and is shown …