Addition of intermittently scanned continuous glucose monitoring to standard care in a cohort of pregnant women with type 1 diabetes: effect on glycaemic control and pregnancy outcomes

The aim of this study was to assess whether the addition of intermittently scanned continuous glucose monitoring (isCGM) to standard care (self-monitoring of blood glucose [SMBG] alone) improves glycaemic control and pregnancy outcomes in women with type 1 diabetes and multiple daily injections.

This was a multicentre observational cohort study of 300 pregnant women with type 1 diabetes in Spain, including 168 women using SMBG (standard care) and 132 women using isCGM in addition to standard care. In addition to HbA_1c, the time in range (TIR), time below range (TBR) and time above range (TAR) with regard to the pregnancy glucose target range (3.5–7.8 mmol/l) were also evaluated in women using isCGM. Logistic regression models were performed for adverse pregnancy outcomes adjusted for baseline maternal characteristics and centre.

The isCGM group had a lower median HbA_1c in the second trimester than the SMBG group (41.0 [IQR 35.5–46.4] vs 43.2 [IQR 37.7–47.5] mmol/mol, 5.9% [IQR 5.4–6.4%] vs 6.1% [IQR 5.6–6.5%]; p=0.034), with no differences between the groups in the other trimesters (SMBG vs isCGM: first trimester 47.5 [IQR 42.1–54.1] vs 45.9 [IQR 39.9–51.9] mmol/mol, 6.5% [IQR 6.0–7.1%] vs 6.4% [IQR 5.8–6.9%]; third trimester 43.2 [IQR 39.9–47.5] vs 43.2 [IQR 39.9–47.5] mmol/mol, 6.1% [IQR 5.8–6.5%] vs 6.1% [IQR 5.7–6.5%]). The whole cohort showed a slight increase in HbA_1c from the second to the third trimester, with a significantly higher rise in the isCGM group than in the SMBG group (median difference 2.2 vs 1.1 mmol/mol [0.2% vs 0.1%]; p=0.033). Regarding neonatal outcomes, newborns of women using isCGM were more likely to have neonatal hypoglycaemia than newborns of non-sensor users (27.4% vs 19.1%; OR_adjusted 2.20 [95% CI 1.14, 4.30]), whereas there were no differences between the groups in large-for-gestational-age (LGA) infants (40.6% vs 45.1%; OR_adjusted 0.73 [95% CI 0.42, 1.25]), Caesarean section (57.6% vs 48.8%; OR_adjusted 1.33 [95% CI 0.78, 2.27]) or prematurity (27.3% vs 24.8%; OR_adjusted 1.05 [95% CI 0.55, 1.99]) in the adjusted models. A sensitivity analysis in pregnancies without LGA infants or prematurity also showed that the use of isCGM was associated with a higher risk of neonatal hypoglycaemia (non-LGA: OR_adjusted 2.63 [95% CI 1.01, 6.91]; non-prematurity: OR_adjusted 2.52 [95% CI 1.12, 5.67]). For isCGM users, the risk of delivering an LGA infant was associated with TIR, TAR and TBR in the second trimester in the logistic regression analysis.

isCGM use provided an initial improvement in glycaemic control that was not sustained. Furthermore, offspring of isCGM users were more likely to have neonatal hypoglycaemia, with similar rates of macrosomia and prematurity to those of women receiving standard care.