ABSTRACT
Background: The differential diagnosis of acute shortness of breath in a pregnant woman with COVID-19 is broad. Pregnancy is a ketosis-prone state, which can result in metabolic acidosis and tachypnoea. Methods: We describe four pregnant women with COVID-19 and breathlessness where ketoacidosis was found to contribute to symptomatic tachypnoea. Results: One patient did not have associated COVID-19 pneumonitis, but presented with severe tachypnoea and metabolic acidosis; three women had pneumonitis and metabolic acidosis. Corrective treatment for the metabolic abnormalities resulted in resolution of the ketoacidosis in all cases. No women had coexistent diabetes. Conclusion: This is the first series of COVID-19 in pregnancy complicated by ketoacidosis and symptomatic tachypnoea. Ketoacidosis associated with COVID-19 is an important cause of tachypnoea requiring specific treatment, which should not be overlooked. Potential mechanisms for this are discussed with a framework for interpretation of blood gas results during pregnancy.