Objectives: The aims of this study were: to evaluate the prevalence of abdominal wall defects in the Polish population, to analyze temporal trends in the prevalence, to identify areas (clusters) of high risk of abdominal wall defects, and to characterize, with respect to epidemiology, children with abdominal wall defects and their mothers in the area defined as a cluster. Material and Methods: We used isolated congenital malformations (gastroschisis Q79.3 and omphalocele Q79.2 according to the International Statistical Classification of Diseases and Related Health Problems, 10th revision (ICD-10, the extended version)) data reported to the Polish Registry of Congenital Malformations (PRCM) over the years 1998– 2008 based on the population of 2 362 502 live births. We analyzed 11 administrative regions of Poland with complete epidemiologic data. Results: Of 11 regions, 2 had a significantly higher standardized prevalence of isolated gastroschisis: Dolnośląskie (1.7/10 000 live births, p = 0.0052) and Śląskie (1.9/10 000 live births, p < 0.0001). Furthermore, within the region of Dolnośląskie, we defined a clear prevalence of the isolated gastroschisis cluster (p = 0.023). We comprehensively examined demographic and socio-economic risk factors for abdominal wall defects in this area, and we found that these factors failed to account for the cluster. Conclusions: We identified a distinct prevalence cluster for isolated gastroschisis, although a precise reason for the disease clustering in this region remains unknown. Cluster identification enables more focused research aimed at identification of specific factors with teratogenic effects.