medwireNews: Continuous glucose monitoring (CGM) metrics show early divergence between pregnant women with type 1 diabetes who subsequently give birth to normal weight versus large for gestational age (LGA) infants, study findings indicate.
“Normal birth weight is associated with achieving significantly lower mean CGM glucose concentration across the 24-[hour] day and higher CGM time in range from before the end of the first trimester, emphasizing the need for a shift in clinical management, with increased focus on using weekly CGM glucose targets for optimizing maternal glycemia from early pregnancy,” write Eleanor Scott (University of Leeds, UK) and co-authors in Diabetes Care.
They analyzed more than 10.5 million CGM glucose measurements from 386 pregnant women with type 1 diabetes who took part in two studies.
The researchers report that, overall, mean CGM glucose concentrations fell sharply during the first 10 weeks of pregnancy while the percentage time in range (TIR) for the pregnancy target of 3.5–7.8 mmol/L (63–140 mg/dL) increased. Both measures then plateaued until 28 weeks’ gestation, before improving further still until delivery.
In addition, the investigators observed that, up to 10 weeks, women who went on to deliver normal weight (10–90th percentile) and LGA (>90th percentile) infants had similar CGM glucose metrics, but after this timepoint significant differences between the two groups emerged.
Specifically, women with normal weight infants had a significantly lower mean CGM glucose concentration from 10 weeks onwards than those with LGA infants (7.1 vs 7.6 mmol/L [128 vs 137 mg/dL), as well as a significantly higher percentage TIR (57 vs 50%).
In line with this, both groups experienced steep reductions in hyperglycemia during the first 10 weeks of pregnancy. After this point, women with normal weight infants spent a significant 5% less time above the target range than those with LGA infants, at 35% versus 40%.
Hypoglycemia, or time below range (TBR), peaked at a rate of approximately 10% at 10 weeks in both groups and then diverged at around 14 weeks. By 30 weeks, the TBR had not fallen below 8% in the women with normal weight infants but had reached 6% in those with babies born LGA.
The women with normal weight infants also had significantly lower 24-hour glucose profiles from 12 weeks’ gestation than those with LGA infants, with a sustained “small but clinically relevant difference” of 0.5 mmol/L (9 mg/dL).
Scott and co-authors conclude that their “results provide unprecedented insight into glucose physiology across gestation and the relationship between CGM glucose levels and birth weight in pregnant women with [type 1 diabetes].”
They add that the “data will inform international clinical guidelines and support patients and clinicians to use CGM more effectively, which will, it is hoped, help to improve glycemia and reduce LGA.”
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