Introduction: The introduction of universal glucose tolerance testing in pregnancy together with revised diagnostic criteria for gestational diabetes mellitus (GDM) resulted in a marked increase in the number of pregnancies complicated by GDM.
Design: Retrospective cohort study of women with gestational diabetes attending for pregnancy care at the Royal Women’s Hospital (RWH), Melbourne, Australia’s largest quaternary level maternity centre.
Method: Women with gestational diabetes attending for antenatal care at RWH between January 2010 and December 2020, were identified from the hospital database. Maternal demographic data, antenatal complications such as hypertensive disease in pregnancy or pre-eclampsia, mode of delivery, birthweight and labour complications were collected.
Results: Our study cohort comprised of 6980 women with GDM. The rate of GDM more than doubled during the 11-year study period with 417 women seen annually in 2010 compared to 923 seen in 2020. Consequently, 13% of our patients attending for pregnancy care in 2020 were diagnosed with GDM. The mean maternal age was 32 years (range 15-55) and the mean parity was 0.91 (range 0-10). All patients received advice on dietary and exercise intervention, and 51% required insulin treatment. Obesity (BMI>35) was more commonly observed in the insulin-dependent group than the diet-controlled group (19% vs 8%). Rates of hypertensive disease, pregnancy-induced hypertension (PIH) and pre-eclampsia (PET), remained stable over the decade and were similar among both, diet and insulin-controlled patients (6% and 7% respectively). The mean gestational age at birth was 37.9 weeks (range 20-42) with 13% giving birth prior to 37 weeks. The mean birthweight was 3191g with similar rates of macrosomia in both groups: overall 6% of infants weighed over 4000g and 1% weighed over 4500g. The rates of Caesarean section were consistently higher in the insulin-controlled group for both nulliparous and multiparous women representing 45% and 49%, compared with 35% and 41% in the diet-controlled group. Overall rates of admission to Neonatal Intensive Care Unit (NICU) and Special Care Nursery (SCN) were similar in both groups with 17% of infants needing newborn care. There were 50 stillbirths and 22 neonatal deaths in the entire cohort of 6980 women with gestational diabetes corresponding to a perinatal mortality rate of 10.3 per 1000 births.
Conclusion: Over the 11-year study period, the rate of GDM diagnosis has increased significantly within the maternity population, causing significant burden to the healthcare systems, increased antenatal attendances and intervention.