Objectives: To review our experience with the prenatal detection of congenital diaphragmatic hernia (CDH) in fetuses presenting for ultrasound screening of chromosomal abnormalities in the first trimester.
Methods: As part of our first-trimester ultrasound protocol, fetuses with a crown-rump length between 45 and 84 mm underwent a limited anatomical assessment in conjunction with nuchal translucency thickness measurement and nasal bone assessment. Cases of CDH diagnosed prenatally or after delivery in this population were identified.
Results: Among the six cases of CDH detected (prevalence of 1 in 927), the first-trimester ultrasound findings were abnormal in five fetuses (83%), including three with increased nuchal translucency only; one with increased nuchal translucency, an intrathoracic stomach, dextrocardia and a cephalocele; and one with normal nuchal translucency thickness and a small, complex intrathoracic mass later confirmed as the fetal stomach. The diagnosis of CDH was confidently made in the first trimester in one case, in the second trimester in three cases, and after birth in the remaining two cases.
Conclusion: The diagnosis of CDH in the first trimester is difficult, especially in those cases in which the defect is small or late migration of the abdominal viscera occurs. Therefore, screening for CDH in the first trimester is unlikely to be effective.