Prevalence of pre-existing diabetes mellitus in pregnancy and associated prescribing patterns using electronic health records

Talk Code: 

The problem

Diabetes mellitus (DM) is one of the commonest chronic conditions affecting pregnancy; 2-5% of pregnancies are affected, with increasing prevalence. Pre-existing DM in pregnancy is related to adverse events for mother and baby, optimal glycaemic control prior and during pregnancy reduces the risk.The objectives of this study were to compare characteristics of pregnant women with and without DM and examine time trends in the prevalence of: DM in pregnancy, and prescribing during pregnancy.

The approach

Pregnant women aged 16 years or over were identified as diabetic via diagnostic Read codes and prescriptions. Women were compared in terms of: age, body mass index (BMI), blood pressure, smoking status, social deprivation score and HbA1c. Prevalence of pre-existing DM and prescriptions were calculated by calendar year and DM type between 1995 and 2012.We used The Health Improvement Network (THIN) primary care database; a database of anonymised electronic GP medical records.


Data from 402,529 pregnancies suggest women with pre-existing DM were: older (median: 30, 31 vs 29 years for type 1 (T1DM), type 2 (T2DM) and non-diabetic), had higher BMI (median: 25.9, 29.9 vs 24.1 kg/m2 for T1DM, T2DM and non-diabetic), and were registered with a general practice for longer than pregnant women without diabetes. Pregnant women with T2DM were more to be: non-smokers (46% vs 43%) and had better glycaemic control prior to pregnancy (median HbA1c 37 vs 65mmol/L likely than T1DM).The prevalence of pre-existing T1DM in pregnancy increased from 3.2 to 5.2 per 1000 pregnancies between 1995 and 2012 and for T2DM the increase was from 0.8 to 8.7 between 1995 to 2008 and then to 22.6 per 1000 pregnancies by 2012.The prevalence of prescribing DM therapy in primary care during pregnancy increased for T1DM and decreased for T2DM between 1995 and 2012. The prevalence of insulin prescribing during T1DM pregnancy increased from 1.2% to 9.5% from 1995 to 2012, for T2DM the decrease was from 6.1% to 4.8% between 1995 and 2012.


Women with T2DM had better glycaemic control prior to pregnancy than T1DM women. The prevalence of both T1DM and T2DM increased in pregnancy, prevalence of T2DM accelerated after 2008. The prevalence of prescribing during pregnancy increased in T1DM and decreased in T2DM pregnancies.Women with T1DM need to be better prepared for pregnancy and receive pre-pregnancy guidance on glycaemic control so that the risk of adverse fetal-maternal pregnancy outcomes is reduced. The prevalence of prescribing diabetic therapies during pregnancy is very low, maximum 9.5% during 2012 to T1DM women. Therefore, it is likely that many pregnant women receive treatment in secondary care during pregnancy.


  • Sonia Coton
  • Irwin Nazareth
  • Irene Petersen