A case of severe starvation ketoacidosis developing during pregnancy is presented. The insulinopenic/insulin-resistant state found during fasting in late gestation predisposes to ketosis. Superimposition of stress hormones, which further augment lipolysis, exacerbates the degree of ketoacidosis. In our patient, gestational diabetes, twin pregnancies, preterm labor, and occult infection were factors that contributed to severe starvation ketoacidosis. Diagnosis was delayed because starvation ketosis is not generally considered to be a cause of severe acidosis, and because the anion gap was not elevated. Improved understanding of the complex fuel metabolism during pregnancy should aid in prevention, early recognition, and appropriate therapy of this condition.