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.