Objective: To determine the prevalence of the most common cystic fibrosis mutations in pregnancies complicated by fetal echogenic bowel by using DNA testing.
Methods: Forty-five pregnancies with fetal echogenic bowel were studied prospectively for cystic fibrosis mutations. Using polymerase chain reaction, DNA from fetal amniocytes (n = 21), fetal blood (n = 5), or parental blood (n = 19) was amplified and tested for delta F508, G551D, G542X, and 621 + 1G-->T cystic fibrosis mutations, which account for about 85% of the mutations in the British population. In selected cases, further mutations were tested according to the parental ethnic background.
Results: Only one of the 26 fetuses screened was heterozygous for cystic fibrosis mutations. Among 38 parental samples screened from the remaining 19 pregnancies, cystic fibrosis mutations were detected in two cases, only one of the parents being a carrier in each case. The prevalence of cystic fibrosis carrier status in fetal and parental samples (1:26 and 1:19, respectively) is within the expected prevalence in the British population (1:25). No fetuses were affected by cystic fibrosis in this series, but five were found to have growth restriction, two trisomy 21, two congenital infection, and two bowel obstruction.
Conclusion: Our results suggest that ultrasonographic detection of fetal echogenic bowel is not associated with an increased prevalence of cystic fibrosis mutations in pregnancies at low risk for this disease.