Introduction Diabetes is the most common pre-existing medical condition in pregnancy in the UK. The global obesity epidemic has led to an increase in the incidence of Type 2 Diabetes in pregnancy and gestational diabetes. Obesity may also affect susceptibility to Type 1 Diabetes.1 Children of diabetic mothers are in turn pre-disposed to Type 2 Diabetes in adult life.2

Objective To determine the prevalence of obesity in diabetics and correlate body mass index (BMI) with pregnancy outcomes.

Results 103 cases were identified. Age range was 15 to 43 years. Gestational diabetes n=45, Type 1 Diabetes n=50 and Type 2 Diabetes n=8. BMI was not recorded in 10 cases. BMI range 22–54.

67% were clinically obese. (Class 1 obesity=30%, Class 2 obesity=23% and Class 3 obesity=14%). 20.4% were overweight. Only 12.6% had BMI of 25 or less. In the Obese group the caesarean section rate was 57% (30% Elective and 27% Emergency). Spontaneous vaginal delivery rate was 31% and 12% had assisted vaginal delivery compared to a caesarean section rate of 50%, Vaginal delivery rate of 38.2% and assisted vaginal delivery rate of 11.8% in the non-obese group.

8% of all babies had intra uterine growth restriction. 45% were normal centile for gestation and 47% were above the 95th centile. (Range 1.7–5.4 kg).

Conclusion Obesity is strongly associated with both pre-existing and gestational diabetes in pregnancy. It appears to confer an even greater risk of operative delivery. A significant proportion of babies were macrosomic.