D

First-trimester HbA1c reflects the mother’s average glycaemia during the critical period of organogenesis, and higher values correlate strongly with an increased rate of congenital malformations, making it the preferred marker for estimating fetal damage risk in diabetic pregnancies [Lucas et al., 1989, PMID 2669494; Nielsen et al., 1997, PMID 9401644]. Blood glucose, urine ketones, or amniotic fluid glucose reflect only transient metabolic status and have no proven predictive value for early fetal anomalies.