Introduction: Guidelines recommend women with gestational diabetes (GDM) should maintain glucose levels (BGL) within a tight target (4-7mmol/l) when approaching partition to prevent fetal complications [1]. Betamethasone (BM) is given as two intramuscular injections 24 hours apart for fetal lung maturation if women are expected to deliver under 34-weeks gestation (38-weeks for planned caesarean section) [2,3].
Hypothesis: BGLs are maintained at the recommended level of 4-7mmol/l following BM in GDM by use of a standard adult intravenous insulin protocol, initiated with BGL >6.5mmol/L.
Methods: Retrospective review of women with GDM who received BM on the antenatal ward of a tertiary hospital in 2015. Capillary glucose levels were analysed for 48 hours following the first dose of BM. Univariate and multivariate analyses were used to evaluate factors associated with glycaemic control. Data is shown as mean±SD or median(IQR).
Results: 36 women met inclusion criteria, with mean age 32±5.6 years, gravida 2(1-3), parity 1(0-2), gestation 33±4 weeks at time of BM. Pre-admission treatment was diet alone (47%), metformin monotherapy (6%), and subcutaneous insulin (47%). Mean capillary BGL for 48 hours post BM was 7.3±1.6mmol/L. 54% of observed BGL readings were >7mmol/l, and 7% were >10mmol/L. In 23/36 women with any BGL readings >10mmol/L, 15 had 3 or more readings >10mmol/L. Estimated time spent with BGL >7mmol/L was 23±9/48hrs. Two hypoglyceamic events (both >3mmol/l) occurred in one women. Delays in BGL measurement were associated with suboptimal control, but other factors, including maternal age, gestation, pre-admission treatment, coprescription of subcutaneous insulin were not associated. Trends included prescription of lower intravenous infusion rates to women already on subcutanoues insulin, and lower insulin infusion rates with poorer control.
Conclusion: This study demonstrated that current practice does not achieve target glycaemia. Women with GDM having BM require a specific protocol [4-6] adapted for the local service.