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.