Comparing Pregnancy Outcomes in Fetal Growth Restriction and Overgrowth in Women with Type 1 Diabetes: A Narrative Review

Background: Several scenarios of abnormal fetal growth develop during pregnancy in women with pregestational diabetes. A trend towards a higher incidence of large-for-gestational-age (LGA) births among women with type 1 diabetes (T1D) is observed worldwide despite novel approaches to maternal glycaemic control. Fetal growth restriction (FGR) is commonly recognised as a severe condition. However, the risk of adverse outcomes in LGA fetuses generally remains underestimated. Methods: We conducted a comparative analysis of pregnancy outcomes across different birthweight categories in pregnancies with T1D based on published data (2001–2026). Results: Interactions between disorders of early placentation, impaired nutrient transfer, fetal overnutrition, and genetic background result in alterations in birthweight and disproportionate fetal adipose tissue deposition. Both FGR and macrosomia are associated with increased risks of adverse perinatal outcomes. Although stillbirth occurs at both extremes of fetal growth, term LGA fetuses may remain particularly vulnerable because routine surveillance methods, including arterial Doppler assessment, fail to identify compromised fetuses with excessive growth. Accelerated fetal growth in T1D pregnancies, when placentation is initially impaired, may cause growth-restricted fetuses to appear appropriate for gestational age (AGA). Routine assessment may classify these vulnerable fetuses as being at low risk of perinatal complications. Disproportionate growth, even among infants classified as AGA, is associated with shoulder dystocia, birth trauma, and operative delivery. Neonatal hypoglycaemia and respiratory disorders remain frequent complications across the spectrum of abnormal fetal growth. Conclusions: Increased glucose variability may explain differences in placental and fetal growth trajectories and the high rate of pregnancy complications in patients with target glycated haemoglobin levels and routine capillary glucose monitoring results. Fetal overgrowth reflects impaired intrauterine development and should be considered a high-risk condition requiring careful consideration of the timing and mode of delivery.