Background Antenatal corticosteroids reduce the incidence of neonatal respiratory distress syndrome in preterm delivery1 but cause acute maternal hyperglycaemia in pregnancies complicated by diabetes. Validated protocols to prevent maternal hyperglycaemia are lacking2,3.
Aim Evaluate the safety and efficacy of a subcutaneous insulin (SC-I) in comparison to intravenous insulin (IV-I) protocol for optimising glucose levels (BGLs) in women with diabetes post-betamethasone administration.
Methods Prospective randomised controlled pilot in-patient study in women with pre-existing (T2DM) and gestational diabetes (GDM) at Royal Prince Alfred Hospital, Sydney. SC-I protocol was stratified by pre-corticosteroid insulin dose utilising supplementary SC-I titrated to predicted maternal hyperglycaemia ± rescue IV-I4. IV-I infusion protocol was titrated to hourly BGLs. Primary outcome was maternal at-target BGL (4.0-8.0 mmol/L) and incidence of maternal hypoglycaemia (BGL <4.0 mmol/L) over 48-h post-betamethasone administration.
Results 19 women (3 T2DM, 4 GDM-diet, 12 GDM-insulin) were randomised to a SC-I (n=13) or IV-I (n=6) protocol in a 9-month period. Total SC-I dose increased by 27% from day 1 to day 2 (Figure 1) with only 4 women requiring rescue IV-I (duration 3 to 12-h). Reduced insulin doses were required for women with intrauterine growth-restriction (IUGR) or pre-eclampsia. There was a non-significant trend for higher mean percent at-target BGLs with SC-I vs IV-I (88.1% vs 81.3%; p=0.055) (Figure 2). The overall rate of hypoglycaemia (BGL <4.0 mmol/L) was higher with SC-I vs IV-I (7 vs 2 women, respectively). Of those, 4 women with SC-I and none with IV-I reported a BGL <3.8 mmol/L, and this was associated with sub-optimal glycaemic control and higher glucose variability pre- and post-betamethasone administration.
Conclusions Either a SC-I or IV-I protocol effectively controlled maternal hyperglycaemia following antenatal corticosteroid administration in pregnancies complicated by diabetes, but the SC-I protocol may achieve more time on-target while minimising labour intensive IV-I. IV-I protocol may be preferable in women with sub-optimal glycaemic control, IUGR or pre-eclampsia to reduce the risk of hypoglycaemia.