OBJECTIVE To compare the risk of fetal overgrowth and preterm delivery in pregnant women with type 1 diabetes (T1D) treated with insulin pumps versus multiple daily injections (MDI) and examine whether possible differences were mediated through improved glycemic control or gestational weight gain during pregnancy. RESEARCH DESIGN AND METHODS The risk of pregnancy and perinatal outcomes were evaluated in a cohort of 2,003 pregnant women with T1D enrolled from 17 countries in a real-world set-ting during 2013–2018. RESULTS In total, 723 women were treated with pumps and 1,280 with MDI. At inclusion (me-dian gestational weeks 8.6 [interquartile range 7–10]), pump users had lower mean HbA_1c (mean ± SD 50.6 ± 9.8 mmol/mol [6.8 ± 0.9%] vs. 53.6 ± 13.8 mmol/mol [7.1 ± 1.3%], P < 0.001), longer diabetes duration (18.4 ± 7.8 vs. 14.4 ± 8.2 years, P < 0.001), and higher prevalence of retinopathy (35.3% vs. 24.4%, P < 0.001). Proportions of large for gestational age (LGA) offspring and preterm delivery were 59.0% vs. 52.2% (adjusted odds ratio [OR] 1.36 [95% CI 1.09; 1.70], P = 0.007) and 39.6% vs. 32.1% (adjusted OR 1.46 (95% CI 1.17; 1.82), P < 0.001), respectively. The results did not change after adjustment for HbA_1c or gestational weight gain. CONCLUSIONS Insulin pump treatment in pregnant women with T1D, prior to the widespread use of continuous glucose monitoring or automated insulin delivery, was associated with a higher risk of LGA offspring and preterm delivery compared with MDI in crude and adjusted analyses. This association did not appear to be mediated by differences in glycemic control as represented by HbA_1c or by gestational weight gain.