AIMS/HYPOTHESIS: The aim of this study was to investigate whether components of the renin-angiotensin system and semicarbazide-sensitive amine oxidase (SSAO) are associated with the development of pre-eclampsia in women with type 1 diabetes. METHODS: This was an observational study of 107 consecutive pregnant women with type 1 diabetes (median duration 16 years [range 1-36 years], HbA(1c) 6.6% [range 4.9-10.5%]) in early pregnancy. At 8, 14, 21, 27 and 33 weeks and once within 5 days postpartum, blood was sampled for measurements of prorenin, renin, angiotensinogen, ACE and SSAO. HbA(1c), blood pressure and urinary albumin excretion were recorded. Pre-eclampsia was defined as blood pressure >140/90 mmHg and proteinuria =300 mg/24 h after 20 weeks. RESULTS: Pre-eclampsia developed in nine women (8%) with longer diabetes duration (median 20 [range 10-32] vs 16 [range 1-36] years, p¿=¿0.04), higher SSAO concentrations (592 [range 372-914] vs 522 [range 264-872] mU/l, p¿=¿0.04) and a tendency towards higher prorenin levels (136 [range 50-296] vs 101 [range 21-316] ng angiotensin I ml(-1) h(-1), p¿=¿0.06) at 8 weeks compared with women without pre-eclampsia. Levels of renin, angiotensinogen and ACE did not differ in the two groups. Throughout pregnancy, prorenin and SSAO levels were 30% (p¿=¿0.004) and 16% (p¿=¿0.04) higher, respectively, in women developing pre-eclampsia. Using multivariate logistic regression analysis, prorenin concentration at 8 weeks was associated with pre-eclampsia (OR 4.4 [95% CI 1.5-13.0], p¿=¿0.007), i.e. an increase of prorenin of 100 ng angiotensin I ml(-1) h(-1) implies a 4.4 times higher risk of subsequent pre-eclampsia. CONCLUSIONS/INTERPRETATION: In type 1 diabetic women with pre-eclampsia, a higher concentration of prorenin in early pregnancy and higher levels of prorenin and SSAO throughout pregnancy were seen.