Association Between HbA1c Levels on Adverse Pregnancy Outcomes During Pregnancy in Patients With Type 1 Diabetes

CONTEXT: Despite optimization of metabolic balance during pregnancy in type 1 diabetes (T1D), maternal–fetal complications remain higher than in the background population. OBJECTIVE: We examined whether there is an association between glycated hemoglobin (HbA1c) levels and these complications. METHODS: Retrospective study of pregnancies in 678 T1D subjects at Lille Hospital (1997-2019). The association between variations in HbA1c levels and complications was examined. The composite criterion (CC) was defined as having at least 1 of the following complications: prematurity, pre-eclampsia, large for gestational age (LGA), small for gestational age (SGA), or cesarean section. RESULTS: Among the 678 births, median preconception HbA1c was 7.2% (55 mmol/mol), 361 were LGA (56%), 29 were SGA (4.5%), and 504 were births without preterm delivery (76.1%). The CC occurred in 81.8%. Higher HbA1c during the first trimester was associated with the CC (OR 1.04; 95% CI 1.02-1.06 per 0.1% increase; P < .001). Higher HbA1c during the third trimester was associated with the CC (OR 1.07; 95% CI 1.03-1.10 per 0.1% increase; P < .001). The group defined by a first trimester Hba1c >6.5% (48 mmol/mol) and a third trimester HbA1c <6% was associated with an increased rate of the CC (OR 2.81; 95% CI 1.01-7.86) and an increased rate of LGA (OR 2.20; 95% CI 1.01- 4.78). CONCLUSION: Elevated HbA1c is associated with maternal–fetal complications. Despite optimization of metabolic balance during the third trimester, for patients with early glycemic imbalance the risk of LGA persists.