Aim To compare maternal characteristics and pregnancy outcomes in twin pregnancies to women with and without pre-gestational diabetes.

Method We analysed data on 27 women with pre-gestational diabetes (54 twins) and 6407 women (12,814 twins) without diabetes from the Northern Survey of Twin and Multiple Pregnancy (NorSTAMP) during 1998–2010. Descriptive statistics were used to compare maternal characteristics between the groups. Adjusted odds ratios (aOR) with 95% confidence intervals (CI) for combined adverse pregnancy outcome (fetal loss <24 weeks, stillbirth, infant death or major congenital anomaly) were calculated using logistic regression.

Results Twin mothers with diabetes were older (p = 0.001) with higher BMIs (p < 0.0001) than those without diabetes. Their twins were more likely to deliver earlier (p = 0.026), by C-section (80.4% vs 49.7%; p < 0.0001), be large for gestational age (p < 0.0001) and require admission to SCBU (p < 0.0001). The extended perinatal mortality rate in twins of mothers with diabetes was 86.9/1000 vs 37.8/1000 births in those without diabetes. Congenital anomaly rates were 92.6/1000 vs 36.9/1000 offspring. The rate of an adverse pregnancy outcome in twins of women with diabetes was significantly higher (RR 1.95, 95% CI 1.18–3.22). Diabetes (aOR 3.40, 95% CI 1.11–10.40), deprivation (aOR 1.57, 95% CI 1.17–2.13), monochorionicity (aOR 3.05, 95% CI 2.42–3.83), an earlier gestation at booking (aOR 0.94, 95% CI 0.94–0.99) and multiparity (aOR 0.60, 95% CI 0.47–0.75) were significant predictor variables.

Conclusion The presence of maternal pre-gestational diabetes was associated with more than three-fold increased risk of adverse pregnancy outcome in twins conferring a similar risk to that of monochorionicity.