Demographic and outcome data
Data were obtained from in-house databases, medical files and the Obstetrix Clinical Database System (http://www.meridianhi.com/index.php/obstetrix), a statewide database that accesses data from the New South Wales Perinatal Data Collection, a population-based surveillance system covering all births in the state. Maternal data collected included age at estimated date of confinement, ethnicity, height, weight at booking-in, week of booking-in, week of diagnosis of GDM, results of the GTT, requirement for and starting date of insulin and/or metformin, mode of delivery and need for instrumental delivery. Preterm birth was defined as delivery before 37 weeks gestation. Early GDM was defined as GDM diagnosed before 22 weeks gestation. Instrumental delivery or emergency Caesarean section were considered adverse delivery outcomes (ADO).
Neonatal data included gestational age at delivery, sex, birth weight, shoulder dystocia and fetal or neonatal death. Birth centiles were calculated using the Perinatal Institute’s customized centile calculator (https://www.gestation.net/birthweight centiles/birthweight centiles.htm) which accounts for maternal height, weight, ethnicity, parity, sex of the child and gestational age at birth, for an Australian population. LGA was defined as a birth weight centile ≥90%, and SGA was defined as a birth weight centile ≤10%. At the RHW, neonatal hypoglycemia was defined as a capillary blood glucose <2.2 mmol/L. At BMDH, neonatal hypoglycemia was recorded if this diagnosis had been entered into the Obstetrix database. The primary adverse neonatal outcomes (ANO) studied were LGA and SGA. In addition, a composite ANO was defined as the presence of at least one of the following: shoulder dystocia, perinatal death, LGA or SGA.