Background: Pregestational diabetes is associated with adverse maternal and perinatal outcomes. Appropriate preconception optimisation and antenatal care may mitigate these risks and have been increasingly emphasised in international and local guidelines. The local impact of increasing awareness of these risks and adoption of recommendations for pre-existing diabetes in pregnancy on maternal and perinatal outcomes is unclear. We aimed to evaluate changes over time in the local characteristics and outcomes of pregnancies complicated by pre-existing diabetes.
Methods: Retrospective analysis of pregnant women with pre-existing type 1 or type 2 diabetes delivering at a single tertiary referral hospital in Western Sydney between 2012 and 2022. Sociodemographic, medical and obstetric data, pre-pregnancy weight and gestational weight gain, first trimester and third trimester HbA1c, total daily insulin requirement at delivery, presence of microvascular complications, and maternal and perinatal outcome data were collected and Poisson regression was used to assess for changes in outcomes over time.
Results: There were 376 pregnancies with pregestational diabetes over the 10 years studied (87 [23.1%] type 1 diabetes and 289 [76.9%] type 2 diabetes with mean diabetes duration 6.6±6.8 years). Age at conception was 32.5±5.7 years with pre-pregnancy BMI 30.2±7.0 kg/m2. Of 340 pregnancies, 63 (18.5%) were complicated by preeclampsia, 3/343 (0.9%) by stillbirth, 26/350 (7.4%) by cardiac congenital anomaly, 94/373 (25.2%) by preterm delivery <37 weeks, 101/364 (27.7%) by large for gestational age (LGA) and 34/364 (9.3%) by small for gestational age (SGA). Pregnancies achieving first trimester HbA1c<6.5% decreased (p<0.001) whereas there were no changes over time in the rate of microvascular complications or preeclampsia. Rate of preterm delivery was 1.09 times less likely each year (p=0.007) and there was a trend towards decreasing SGA (β=0.9, p=0.056). There were no significant changes over time in cardiac congenital anomaly, LGA or neonatal hypoglycaemia (glucose<2.6mmol/L).
Summary: Type 2 diabetes comprised the majority of pregnancies in this 10-year analysis of pre-existing diabetes in pregnancy. Preterm delivery decreased over time but there were no significant changes in other maternal and perinatal outcomes.