Introduction:

Pregnancies affected by Type 1 (T1DM) and Type 2 diabetes (T2DM) have been associated with poorer obstetric outcomes. To complement current Australian literature, we conducted an exploratory 10-year retrospective study of a single tertiary obstetric hospital exploring multiple associations of established predictive factors with pregnancy outcomes in women with pre-existing diabetes.

Methods:

Clinical and biochemical characteristics of women with T1DM(n=93) and T2DM(n=106) between 2004-2014 were recorded. Group comparisons were performed using independent-samples t-tests and chi-square tests. Multivariable logistic regression models were formulated for major obstetric outcomes (pre-eclampsia, pre-term birth, neonatal intensive care admission, large/small for gestational age, Apgar<7 at 5minutes, neonatal hypoglycaemia) as dependent variables,and estimated Glomerular Filtration Rate (eGFR) using Chronic Kidney Disease Epidemiology Cohort formula, blood pressure, HbA1c, age, type of diabetes, and BMI as independent variables throughout pregnancy. Due to the exploratory nature of the study, no correction for multiple testing was undertaken.

Results:

Compared to women with T2DM, neonatal outcomes were poorer in T1DM including large for gestational age (65% vs.36%; p < 0.0001) and macrosomia defined as > 4000g (25% vs.6%; P<0.0001). HbA1C was 7.1% ±1.0% vs. 6.5% ±0.8% (p=0.02) in T1DM and T2DM respectively. Risk of the other major outcomes was similar. The overall proportion of pre-eclampsia was 15% (comparison to 5% in the general population). There were 2 fetal deaths in utero in T1DM and 3 in the T2DM group.

For the pooled analysis, median HbA1c was 6.5±0.95% (47mmol/mol). Higher HbA1c in the third trimester was associated with large for gestational age (OR1.9, p=0.04 95CI 1.05-3.45).No association with other major adverse outcomes was detected with HbA1c.Mean blood pressure was 119/72±11/7mmgHg.Higher mean systolic blood pressure throughout pregnancy, was associated with a higher risk of developing pre-term birth<37 weeks (p=0.01). Higher diastolic blood pressure during second trimester was associated with a higher risk of pre-eclampsia  (p=0.01). Association between eGFR with pre-eclampsia and pre-term birth< 32 weeks was detected.

Conclusion:

Despite relatively good overall blood pressure and reasonable glycaemic control, unfavourable outcomes remain high in pregnant women with pregestational diabetes. Although observational, these data may be helpful for counselling women with diabetes regarding pregnancy outcomes.