Aims/hypothesis: Continuous subcutaneous insulin infusion by insulin pump is often superior in improving glycaemic control compared with conventional multiple daily insulin injection (MDI). However, whether pump treatment leads to improved pregnancy outcomes in terms of congenital malformations and perinatal death remains unknown. The present aim was to evaluate the risk of malformations and perinatal and neonatal death in pregnant women with type 1 diabetes treated with pump or MDI. Methods: We performed a secondary analysis of a prospective multinational cohort of 2088 pregnant women with type 1 diabetes in a real-world setting who were treated by pump (n=750) or MDI (n=1338). ORs for offspring with congenital malformations or perinatal or neonatal death were calculated using crude data and by logistic regression on propensity score-matched data. Results: At enrolment (gestational week 8; 95% CI 4, 14), pump users had a higher educational level (university degree: 37.3% vs 25.1%; p<0.001) and better glycaemic control (mean HbA_1c: 51±10 mmol/mol [6.8±0.9%] vs 54±14 mmol/mol [7.1±1.3%], p<0.001) compared with MDI users. Moreover, a greater proportion of pump users had an HbA_1c level below 75 mmol/mol (9%) (97.6% vs 91.9%, p<0.001), and more often reported taking folic acid supplementation (86.3% vs 74.8%; p<0.001) compared with MDI users. All clinically important potential confounders were balanced after propensity score matching, and HbA_1c remained lower in pump users. The proportion of fetuses with at least one malformation was 13.5% in pump users vs 11.2% in MDI users (crude OR 1.23; 95% CI 0.94, 1.61; p=0.13; propensity score-matched (adjusted) OR 1.11; 95% CI 0.81, 1.52; p=0.52). The proportion of fetuses with at least one major malformation was 2.8% in pump users vs 3.1% in MDI users (crude OR 0.89; 95% CI 0.52, 1.51; p=0.66; adjusted OR 0.78; 95% CI 0.42, 1.45; p=0.43), and the proportions of fetuses carrying one or more minor malformations (but no major malformations) were 10.7% vs 8.1% (crude OR 1.36; 95% CI 1.00, 1.84; p=0.05; adjusted OR 1.23; 95% CI 0.87, 1.75; p=0.25). The proportions of perinatal and neonatal death were 1.6% vs 1.3% (crude OR 1.23; 95% CI 0.57, 2.67; p=0.59; adjusted OR 2.02; 95% CI 0.69, 5.93; p=0.20) and 0.3% vs 0.3% (n=2 vs n=4, p=not applicable), respectively. Conclusions/interpretations: Insulin pump treatment was not associated with a lower risk of congenital malformations, despite better glycaemic control in early pregnancy compared with MDI. Further studies exploring the efficacy and safety of pump treatment during pregnancy are needed. Graphical abstract: [Figure not available: see fulltext.]