HbA1c Levels Are Significantly Lower in Early and Late Pregnancy

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Abstract
Strict glycemic control is essential to minimize the maternal and fetal morbidity and mortality of pregnancies complicated by diabetes (1–3). In addition to home blood glucose measurement, which may not always reflect the true average blood glucose level (4), HbA1c is a useful parameter in metabolic regulation (5–8). Thus, supplementation with HbA1c, as is common outside pregnancy, seems appropriate. Before pregnancy, the target for metabolic control in women with diabetes is HbA1c values near the normal range (9). However, the upper normal range of HbA1c during normal pregnancy is only sparsely investigated with different methods (10), mainly in late pregnancy (5,6,11,12), and reference ranges are generally established from the nonpregnant state (4). Increased third-trimester HbA1c levels are associated with an increased risk of preeclampsia (3,13), macrosomia (1), and stillbirth (2), leading to speculations that the target for HbA1c in pregnancy should be even lower than outside pregnancy to prevent adverse events. There is a need to establish the reference range of HbA1c during normal pregnancy with an internationally recognized Diabetes Control and Complications Trial (DCCT)-aligned method. In this study, we evaluated the normal upper range of HbA …