here were no statistically significant interactions identified between maternal BMI and gestational diabetes for the clinical outcomes of interest, except for gestational age at delivery (GA) (Table 2). Women who were obese were significantly more likely to require caesarean birth (RR 1.27; 95% CI 1.07 to 1.50; p = 0.006), and deliver a large for gestational age (LGA) infant (RR 1.38; 95% CI 1.07 to 1.77; p = 0.01), independent of GDM. Women who were diagnosed with gestational diabetes were significantly less likely to give birth to an infant with birth weight above 4 kg (RR 0.60; 95% CI 0.36 to 0.1.00; p = 0.05), independent of BMI ( Fig. 2). Both women who were obese and those who had GDM were more likely to deliver at an earlier gestational age, and the interaction between GDM and obesity was significant (0.005). The reduction in gestational age attributable to GDM and obesity was similar. Induction of labour was not significantly increased regardless of BMI or GDM. Infants of women who were diagnosed with GDM were more likely to require admission to the neonatal intensive care unit (NICU) (RR 2.41; 95% CI 1.04, 5.61; p = 0.04), independent of maternal BMI. There was a trend towards increased admission to NICU in the infants of women who were obese (RR 2.42; 95% CI 0.98 to 5.99; p = 0.06) compared with women who were overweight, independent of GDM.