Population-based analysis of left- and right-sided diaphragmatic hernias demonstrates different frequencies of selected additional anomalies†

Congenital diaphragmatic hernia (CDH) is a common birth defect that can be subdivided into several different types depending on the anatomical structures affected. Several studies have demonstrated that right-sided CDH (R-CDH) and left-sided CDH (L-CDH) in humans are associated with different clinical presentations and outcomes. We hypothesized that R-CDH and L-CDH are phenotypically and pathogenically distinct, and that the frequency of associated anomalies would differ among patients with R-CDH compared to patients with L-CDH. Using population-based data from ongoing studies in the California Birth Defects Monitoring Program (CBDMP), we compared 146 CDH cases, 38 with R-CDH (26%) and 108 with L-CDH (74%). The frequencies of atrial septal defect (1/38 R-CDH and 20/108 L-CDH cases; P = 0.015), bilateral pulmonary hypoplasia (22/108 L-CDH cases and 15/38 R-CDH cases; P = 0.029), abnormal skull or facial shape (17/108 L-CDH patients and 1/38 R-CDH cases; P = 0.043), assorted digital anomalies excluding syndactyly, polydactyly or absence of a digit (13/108 L-CDH patients and 0/38 R-CDH patients; P = 0.021) and assorted limb anomalies excluding limb reduction defects (18/108 L-CDH patients and 0.38 R-CDH patients; P = 0.004) all showed a statistically significant difference in frequency between R- and L-CDH patients. This descriptive epidemiological study using newborn surveillance data represents the largest comparison of right and left-sided CDH patients so far performed. Several anomalies as listed above were noted to be different in frequency between R- and L-CDH patients, although the interpretation of the significant variability in the frequency of these anomalies is not yet established and the findings require replication. Birth defects monitoring programs can provide the interface for epidemiology and clinical genetics, which in this case, may generate hypotheses to establish the pathogenesis of CDH laterality. © 2007 Wiley-Liss, Inc.