Introduction: Antenatal glucocorticoids reduce neonatal respiratory morbidity when given prior to pre-term birth (1). In patients with diabetes, antenatal glucocorticoids can induce transient maternal hyperglycaemia for approximately 72 hours. (2) This may be associated with adverse outcomes, including neonatal hypoglycaemia (3-4), prompting recommendations for prophylactic increases in insulin by some expert groups (5). However, there are no validated protocols. A review of our institutional practice of empiric dose escalation (Day 1:25%, Day 2-3:40%, Day 4:20%, Day 5:10%) determined it was inadequate to prevent hyperglycaemia. Internationally, the percentage increase in daily dose varies widely between 40-230% (2, 6-7). We sought to investigate the efficacy of an intensified insulin escalation protocol in achieving time in target range (3.9-7.8mmol/L) within 72 hours post betamethasone administration.
Methods: Following implementation of the intensified insulin escalation protocol at Western Health (Day 1-2: 50% increase , Day 3:30% increase), a prospective cohort study was conducted of the first 30 pregnant women with insulin-treated diabetes requiring betamethasone (Two doses of 11.4mg 24 hours (+/-4 hours) apart). Clinician discretion was allowed per standard care. Data was collected from the electronic medical record. Capillary blood glucose monitoring was recorded in patients with gestational diabetes (GDM)/Type 2 diabetes mellitus (T2DM) and continuous glucose monitoring in Type 1 diabetes mellitus (T1DM). Normally-distributed data was expressed as mean ± standard deviation (SD) and non-normally-distributed data as median (interquartile range (IQR)).
Results: 30 women (80% GDM, 16.7% T2DM, 3.3% T1DM) were included with median gestation 33+2 (30-34+6) weeks at first-dose betamethasone and median BMI 30kg/m2 (27-39 IQR). In the 72 hours post first-dose betamethasone, proportion of readings in-target range (3.9-7.8mmol/L) was 64.2% and proportion of time-above-target range (>7.8mmmol/L) was 34.4%. Hypoglycaemia was rare; 1.3% time < 3.9mmol/L, 0.2% <3.5mmol/L. Median peak glucose was 10.1mmol/L (IQR 8.7-12mmol/L), occurring at 26.9 hours (IQR 10.3-32.1mmol/L) post first-dose betamethasone. Median increase in insulin requirement was 50% (22.6-100% IQR) on Day 1, 100% on Day 2 (35-262% IQR) and 133% on Day 3 (24-400% IQR). Neonatal hypoglycaemia was common (44.4% (12/27).
Conclusion: A significant increase in insulin requirements occurs within 72 hrs of antenatal betamethasone in women with diabetes. Our intensified insulin escalation protocol, although stronger than those previously reported, was insufficient to avoid maternal hyperglycaemia and consequent neonatal hypoglycaemia. We plan to prospectively study a further modified protocol utilising continuous glucose monitoring to determine the optimal protocol for reducing maternal hyperglycaemia, whilst avoiding maternal and neonatal hypoglycaemia.