Continuous glucose monitoring (CGM)
At the recruitment visit in the first trimester of pregnancy (9-13 weeks
gestational age), participants will be first randomized to have either a
blinded CGM sensor (sensor without a reader) (FreeStyle® LibreTM, Abbott
Diabetes Care, Alameda, CA) or a non-blinded sensor (sensor with a
reader) (FreeStyle Libre Pro ®, Abbott Diabetes Care, Alameda, CA)
inserted on the back of either right or left upper arm on day 0, and
worn up to 14 days. Glucose levels will be recorded from the
interstitial fluid every 15 minutes, CGM data were downloaded from the
reader for the blinded sensors, or using a software, LibreView for the
non-blinded sensor users. Participants were inserted with a new sensor
at the second trimester (18-23 weeks of gestational age) clinic visit.
Only data from the non-blinded sensor with 70% of data captured using
the sensor was used for analysis 20. The following
variables were calculated from CGM readings for each participant: Mean
amplitude of glycaemic excursion (MAGE), Standard deviation of blood
glucose (SDBG), Mean of daily
continuous 24 h blood glucose (MBG), % Coefficient of variation (CV),
% of time spent in glucose target ranges and the J-Index. The % of
time in target ranges were defined as: %TIR (3.5–7.8 mmol/L), %TAR
(>7.8mmol/L, and %TBR (<3.5mmol/L)9. J-index, is a parameter of glucose control21, while MAGE, quantifies major swings of glycaemia
and excludes minor ones was considered the gold standard for assessing
intra-day glycaemic variability 22 . Extracted CGM
data was used to calculate MBG, SDBG, MAGE, %CV and J-Index by an
automated Software EasyGV version 9.0.R2.