Benefits and harms associated with an increase in gestational diabetes diagnosis in Queensland, Australia: a retrospective cohort comparison of diagnosis rates, outcomes, interventions and medication use for two periods, 2011–2013 and 2016–2018, using a large perinatal database

OBJECTIVES: To assess benefits and harms arising from increasing gestational diabetes (GDM) diagnosis, including for women with normal-sized babies. DESIGN, SETTING AND PARTICIPANTS: Diagnosis rates, outcomes, interventions and medication use are compared in a retrospective cohort study of 229 757 women birthing in public hospitals of the Australian State of Queensland during two periods, 2011–2013 and 2016–2018, using data from the Queensland Perinatal Data Collection. OUTCOME MEASURES: Comparisons include hypertensive disorders, caesarean section, shoulder dystocia and associated harm, induction of labour (IOL), planned birth (PB), early planned birth <39 weeks (EPB), spontaneous labour onset with vaginal birth (SLVB) and medication use. RESULTS: GDM diagnosis increased from 7.8% to 14.3%. There was no improvement in shoulder dystocia associated injuries, hypertensive disorders or caesarean sections. There was an increase in IOL (21.8%–30.0%; p<0.001), PB (36.3% to 46.0%; p<0.001) and EPB (13.5%–20.6%; p<0.001), and a decrease in SLVB (56.0%–47.3%; p<0.001). Women with GDM experienced an increase in IOL (40.9%–49.8%; p<0.001), PB (62.9% to 71.8%; p<0.001) and EPB (35.3%–45.7%; p<0.001), and a decrease in SLVB (30.01%–23.6%; p<0.001), with similar changes for mothers with normal-sized babies. Of women prescribed insulin in 2016–2018, 60.4% experienced IOL, 88.5% PB, 76.4% EPB and 8.0% SLVB. Medication use increased from 41.2% to 49.4% in women with GDM, from 3.2% to 7.1% in the antenatal population overall, from 3.3% to 7.5% in women with normal-sized babies and from 2.21% to 4.38% with babies less than the 10th percentile. CONCLUSION: Outcomes were not apparently improved with increased GDM diagnosis. The merits of increased IOL or decreased SLVB depend on the views of individual women, but categorising more pregnancies as abnormal, and exposing more babies to the potential effects of early birth, medication effects and growth limitation may be harmful.