Morbidity and mortality are high in congenital diaphragmatic hernia. Some tools help to predict survival, both prenatally (observed/expected lung-to-head ratio [OELHR], presence of the liver in the chest) and postnatally (Congenital Diaphragmatic Hernia Study Group [CDHSG] score). Our objective was to identify the risk factors associated with mortality and estimate the risk-adjusted mortality in the prenatal period in the subgroup of patients with isolated left-sided hernia. Retrospective and analytical study of patients born at Hospital Italiano de Buenos Aires between 2011 and 2018. A multivariate analysis was done to assess mortality-associated risk factors. For riskadjusted mortality in the prenatal period, the ratio between the observed mortality and the mean "expected" mortality based on the OELHR was estimated. A total of 53 patients were included. Their median gestational age was 38 weeks, and their mean birth weight was 3054 g. Isolated hernia was observed in 73 % of patients. Overall mortality was 45 %, and higher in patients with associated malformations. In the multivariate analysis, the presence of severe pulmonary hypertension estimated by postnatal echocardiogram was independently associated with mortality (adjusted odds ratio: 6.4, 95 % confidence interval: 1.02-40). The observed overall mortality in patients with isolated left-sided hernia was similar to that expected (ratio: 1.05). Overall mortality was similar to that expected based on the OE-LHR. In our population, severe pulmonary hypertension after birth was a determining factor of mortality.