Increased insulin resistance in pregnancy is an expected phenomenon and internationally rates of gestational diabetes and high insulin requirements in the setting of pre-existing diabetes are increasing. However, in some cases insulin resistance becomes severe, resulting in extremely high insulin requirements and creating challenges for patient management. Some medical and underlying genetic conditions are associated with increased tendency towards insulin resistance. In some patients presenting with severe hyperglycaemia or unexpectedly high insulin requirements in pregnancy, investigation of underlying conditions should be considered. Here, we present two cases of severe insulin resistance in pregnancy. In the first patient, a new diagnosis was made of two insulin receptor (INSR) gene mutations (type A insulin resistance, TAR), exacerbated by features of metabolic syndrome. The second patient, a case of known SHORT syndrome with associated lipodystrophy without prior diabetes, developed a sudden high insulin requirement after exposure to exogenous steroids in pregnancy. To date, no cases of SHORT syndrome in pregnancy have ever been described and few case reports exist of patients with INSR mutations in pregnancy. We describe the presentation and the management strategies for each patient and the investigations leading to the diagnosis of Patient 1. The cases serve as a reminder to consider differential diagnoses for severe insulin resistance presenting in pregnancy, provide insights into management strategies for such patients, and highlight a need for future research regarding additional treatment options for patients with refractory hyperglycaemia.