Objective
Continuous glucose monitoring (CGM) devices provide individualised time in range (TIR) data for the diabetic wearer. Optimising the TIR to >70% in pregnant individuals with type-1 diabetes mellitus (T1DM) is recommended by the International Consensus (Diabetes Care, 2019); however, such targets can be difficult to achieve. While improved glycaemic control is hypothesised to improve maternal and foetal outcomes, there is a paucity of local data pertaining to Australian centres. We aim to investigate the relationship between TIR and neonatal outcomes in pregnant individuals with T1DM.
Study design
This was a retrospective study of pregnant individuals with T1DM using CGM who delivered at our single tertiary centre on the Central Coast of New South Wales between January 2020 to December 2023. A range of neonatal and maternal outcomes were included in the analysis, including a composite neonatal variable of macrosomia, phototherapy requirement, special care nursery (SCN) admission, and shoulder dystocia. TIR data was analysed with a cut-off of 60% based on lower average TIR for our local study cohort.
Results
During the study period, 36 pregnancies met inclusion criteria, of which 32 had TIR data. There was high incidence for admission to SCN (31/35, 89%), neonatal hypoglycaemia (27/35, 77%), neonatal jaundice (18/35, 51%), and induction of labour (17/36, 47%). During the second and third trimesters, median TIR was 56.5%; 19 patients (59%) had average TIR<60% and 13 (41%) had TIR≥60%. The composite neonatal outcome was met in 19/19 (100%) of pregnancies with TIR<60% compared to 10/13 (76.9%) with TIR≥60% (p=0.028). Admission to SCN occurred in 18/19 (95%) patients with TIR<60% compared to 9/12 (75%) for those with TIR≥60% (p=0.110); with 2/18 (11%) admissions to the neonatal intensive care for TIR<60% compared to 0/12 for TIR≥60% (p=0.232). Neonatal hypoglycaemia requiring intravenous glucose occurred in 13/19 (68%) pregnancies with TIR<60% compared to 6/13 (46%) with TIR≥60% (p=0.208). Mean head circumference trended higher with TIR<60% (35.2cm) compared to TIR≥60% (34.0cm) (p=0.086). Notably, patients with TIR<60% attended fewer endocrine appointments, 5.4, on average in their third trimester compared to those with TIR≥60%, 7.6 (p=0.020).
Conclusion
Our results demonstrate a high incidence of neonatal complications associated with T1DM pregnancies on the Central Coast, with relatively low average TIR during the second and third trimesters. Our results suggest a possible link between higher average TIR and reduced neonatal complications, and indicates that greater specialist engagement later in pregnancy can improve TIR.