Methods
The ATLANTIC Diabetes in Pregnancy Group (ATLANTIC DIP) consists of a
number of antenatal centres along the Irish Atlantic seaboard and offers
pre-pregnancy, antenatal and postnatal care to women with
pre-gestational diabetes and GDM. Patient information is recorded in
real time on the diabetes information system (DIAMOND, Hicom Woking,
UK).
This current study is a
retrospective cohort study of pregnancy outcomes for obese GDM women
recorded in the Atlantic DIP database over a 7-year period, 2010 to
2016. Out of a total of 1319 women with GDM diagnosed according to
International Association of the Diabetes and Pregnancy Study
Groups (IADPSG) criteria and treated either with medical nutritional
therapy (GDM-D) only or diet and insulin (GDM-I), we identified 754
women with a BMI ≥30 kg/m2.
Women were stratified according to
their GWG status into three distinct groups; Group 1: women with weight
loss and/or weight gain of <5kgs (n= 237); GDM- D (n=91);
GDM-I (n= 146); Group 2: women with weight gain of 5-9kgs (n= 77); GDM-D
(n=29); GDM-I (n=48); and group 3: women with weight gain
>9kgs (n= 440); GDM-D (n=159), GDM-I (n=281),
(Figure 1 and Table 1).
The IADPSG criteria confirm a diagnosis of GDM when fasting glucose is
≥5.1 mmol/L (92 mg/dL), 1-hour glucose is ≥10.0 mmol/L (180mg/dL) or
2-hour glucose is ≥8.5 mmol/L (153mg/dL) following a standard 2 hours
75-g OGTT. Women diagnosed with GDM are managed in a combined diabetes
antenatal clinic and reviewed every 2-4 weeks by a multidisciplinary
team including an obstetrician, diabetologist, and midwife/diabetes
nurse specialist. Each patient receives a consultation on diet changes
at GDM diagnosis and additional consultations as required. During this
consultation, the patient receives advice about carbohydrate intake and
distribution. This is supplemented by written material and online access
to other materials for consolidation of dietary advice. In addition,
women have access by phone to a midwife/diabetes nurse specialist for
advice during the standard working week.
BMI was calculated at first antenatal visit
(weeks 11-14 of pregnancy) and
stratified according to WHO guidelines as underweight (<18.5
kg/m2), normal weight (18.5-24.9
kg/m2), overweight (25-29.9 kg/m2),
and obese (≥30 kg/m2). Weight was measured at each
clinic visit by the attending physician as per the local best practice
weight measurement guidelines.
Consistent with local evidence-based guidelines, women are advised to
monitor their blood glucose levels 7 times per day (fasting, pre-meals,
1-hour post meals, and at bedtime). Blood glucose targets are set at
≤5.3 mmol/L (95 mg/dL) for fasting / pre-meal, and ≤7.8 mmol/L (140
mg/dL) 1-hour post meals. Insulin is commenced when blood glucose
readings are outside these ranges on more than 3 successive days. Women
are commenced on a long acting analogue insulin (insulin detemir)
titrating the dose every 3 days to achieve a fasting blood glucose level
of ≤5.3 mmol/L (95mg/dL) and a short acting analogue insulin (insulin
aspart) to achieve 1h post prandial blood glucose level ≤7.8 mmol/L (140
mg/dL).
The following maternal outcomes: caesarean section (CS), preeclampsia
(PET),pregnancy induced hypertension (PIH), polyhydramnios, ante partum
haemorrhage (APH) and post-partum haemorrhage (PPH) and infant outcomes:
congenital malformations, neonatal mortality, admission to the Neonatal
Intensive Care Unit (NICU), prematurity, large for gestational age
(LGA), macrosomia, SGA, neonatal hypoglycaemia, respiratory distress and
shoulder dystocia are recorded. PET is defined as new onset systolic
blood pressure (SBP) of at least 140 mmHg and/or diastolic blood
pressure (DBP) of at least 90 mmHg at more than 20 weeks gestation with
proteinuria of greater than 300 mg/day. PIH is defined as new-onset BP
at least 140/90mmHg after 20 weeks gestation with no proteinuria.
Prematurity is defined as a baby born alive before 37 completed weeks of
pregnancy. Mortality includes stillbirth and neonatal death. LGA is
defined as an infant birth weight greater than the 90th percentile for
sex and gestational age plotted on
the WHO growth chart and macrosomia as an infant birth weight greater
than 4000g. SGA is defined as an infant birth weight less than the 10th
percentile for sex and gestational age
plotted on the WHO growth chart.
Neonatal hypoglycaemia is defined
as a plasma glucose level of less than 1.65 mmol/L (30 mg/dL) in the
first 24 hours of life and less than 2.5 mmol/L (45 mg/dL) thereafter.
The decision to proceed with a caesarean delivery is made by the woman’s
obstetrician. Polyhydramnios is diagnosed when the amniotic fluid index
measured is greater than 24cm on foetal ultrasound. Shoulder dystocia is
defined as a vaginal cephalic delivery that requires additional
obstetric manoeuvres to deliver the foetus after the head has delivered
and gentle traction has failed.
Statistical analysis
Data were analysed using SPSS version 20 (Armonk, NY, IBM Corp). No
imputations were carried out for missing data. The Kolomogorov-Smirnov
test was used to evaluate data distribution. Differences in normally
distributed data between the two groups were assessed by the independent
t-test, with the Mann-Whitney U test used for non-normally distributed
data. Chi-square was used for qualitative data to compare the two
groups. Multivariate analysis was performed using multiple logistic
regression to model relationships
between less than recommended GWG
(reference group: women with the IOM recommended GWG (Group 2)) and
maternal and infant outcomes, correcting for age, smoking status,
ethnicity, and family history of diabetes (first-degree relatives).
Differences between the two groups were reported in adjusted odds ratio
(aOR) and 95% confidence interval (CI). A p<0.05 was deemed
statistically significant.
Three-way ANOVA/ Kruskall Wallis
were used to assess the differences in baseline characteristics and
pregnancy outcomes between women with insufficient GWG, the IOM
recommended GWG and excessive GWG.