Pregnancy outcomes in women with type 1 diabetes remain strongly influenced by small shifts in glucose control. Findings from a study presented at the European Association for the Study of Diabetes (EASD) 2025 highlight how maternal glycemic patterns shape newborn size.

The analysis included 173 pregnant women with type 1 diabetes, all managed with sensor-augmented insulin pumps from the first trimester. While most participants maintained good control, with median HbA1c values below 6.3% and time-in-range (TIR) above 70%, 32% of pregnancies still resulted in large-for-gestational-age (LGA) infants.

Compared with mothers of appropriate-for-gestational-age newborns, those with LGA outcomes had higher HbA1c in the second and third trimesters and consistently lower TIR. Insulin data revealed an additional signal: mothers of LGA infants required higher basal insulin doses at several points, especially from weeks 14 to 36, leading to a higher basal-to-bolus ratio.

These findings suggest that modest increases in HbA1c and basal insulin demand may predict excessive fetal growth, underscoring the importance of close monitoring and individualized therapy during pregnancy.