Fetal bowel anomalies may reveal cystic fibrosis (CF) and the search for CF transmembrane conductance regulator (CFTR) gene mutations is part of the diagnostic investigations in such pregnancies, according to European recommendations. We report on our 18-year experience to document comprehensive CFTR genotypes and correlations with ultrasound patterns in a series of 694 cases of fetal bowel anomalies. CFTR gene analysis was performed in a multistep process, including search for frequent mutations in the parents and subsequent in-depth search for rare mutations, depending on the context. Ultrasound patterns were correlated with the genotypes. Cases were distinguished according to whether they had been referred directly to our laboratory or after an initial testing in another laboratory. A total of 30 CF fetuses and 8 cases compatible with CFTR-related disorders were identified. CFTR rearrangements were found in 5/30 CF fetuses. 21.2% of fetuses carrying a frequent mutation had a second rare mutation, indicative of CF. The frequency of CF among fetuses with no frequent mutation was 0.43%. Correlation with ultrasound patterns revealed a significant frequency of multiple bowel anomalies in CF fetuses. The results emphasize the need to search for rearrangements in the diagnosis strategy of fetal bowel anomalies. The diagnostic value of ultrasound patterns combining hyperechogenic bowel, loop dilatation and/or non-visualized gallbladder reveals a need to revise current strategies and to offer extensive CFTR gene testing when the triad is diagnosed, even when no frequent mutation is found in the first-step analysis.

Grade III fetal bowel hyperechogenicity and/or loop dilatation observed at the second trimester of pregnancy can be due to several disease conditions, including cystic fibrosis (CF). Screening for frequent CF mutations is performed as a first step and, in certain situations, such as when a frequent CF mutation is found in the fetus, the increased risk of CF justifies an in-depth study of the second allele. To determine the contribution of large CFTR gene rearrangements in such cases, detected using a semiquantitative fluorescent multiplex PCR (QFM-PCR) assay, we collated data on 669 referrals related to suspicion of CF in fetuses from 1998 to 2009. Deletions were found in 5/70 cases in which QFM-PCR was applied, dele19, dele22_23, dele2_6b, dele14b_15 and dele6a_6b, of which the last three remain undescribed. In 3/5 cases, hyperechogenicity was associated with dilatation and/or gallbladder anomalies. Of the total cases of CF recognized in the subgroup of first-hand referrals, deletions represent 16.7% of CF alleles. Our study thus strengthens the need to consider large CFTR gene rearrangements in the diagnosis strategy of fetal bowel anomalies, in particular in the presence of multiple anomalies.

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