<p>We investigated significant congenital cardiovascular malformations (CCVM) in Nevada, accompanied by declining birth rates. We identified those diagnosed pre- and postnatally in Nevada with significant CCVM between January 2012 and December 2024. We defined significant CCVM as cases that underwent or were likely to undergo a surgical or interventional cardiac catheterization procedure between 0 and 24 months of age. We excluded those with a secundum atrial septal defect or patent ductus arteriosus. We identified 1573 cases. Of the 1573, 1427 were live born. Of the 1573, 1486 (94%) had prenatal care. Of the 1486 with prenatal care, 1056 (71%) were prenatally diagnosed, and the prenatal detection rate rose from 53% in 2012 to 91% in 2024 (<i>p</i> &lt; 0.001). During the same period, the Nevada birth rate fell from 12.7 to 9.9 per 1,000 population (<i>p</i> &lt; 0.001). However, the overall prevalence of significant CCVM increased from 272 to 430 per 100,000 live births (<i>p</i> &lt; 0.001). Simultaneously with the declining birth rates, we found, in those prenatally diagnosed with significant CCVM, a statistically significant increase in the percentage of pregnant mothers with comorbidities, increasing from 56% to 85%, <i>p</i> = 0.002. In Nevada, concurrent with declining birth rates, we found an increasing prevalence of significant CCVM. The increasing prevalence of significant CCVM was associated with a simultaneous increase in the percentage of comorbidities in the maternal population.</p>