HbA1c Levels Are Significantly Lower in Early and Late Pregnancy

S trict glycemic control is essential tominimize the maternal and fetalmorbidity and mortality of pregnan-cies complicated by diabetes (1–3). In addition to home blood glucose measure-ment, 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 preg-nancy, seems appropriate. Before pregnancy, the target for met-abolic 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 meth-ods (10), mainly in late pregnancy (5,6,11,12), and reference ranges are gen-erally established from the nonpregnant state (4). Increased third-trimester HbA1c levels are associated with an increased risk of preeclampsia (3,13), macroso-mia (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 refer-ence range of HbA1c during normal preg-nancy with an internationally recognized Diabetes Control and Complications Trial (DCCT)-aligned method. In this study, we evaluated the normal upper range of HbA1c in early and late pregnancy. RESEARCH DESIGN AND METHODS — From our antenatal clinic, we randomly selected 100 healthy pregnant women without previous gesta-tional diabetes (early pregnancy group). All subjects had a random capillary blood glucose level 7.0 mmol/l at their first antenatal visit at approximately week 14 (range 8–17), and none developed gesta-tional diabetes. A selective screening based on risk factors for gestational dia-betes was used (14). A late pregnancy group was estab-lished of 98 healthy pregnant women in week 33 (range 28–37), who, as part of another study (14), had a normal 75-g oral glucose tolerance test (OGTT). HbA1c was measured on the same day as the OGTT. The nonpregnant control group con-sisted of 145 healthy women aged 30 years who were investigated as a part of the population survey Inter 99 (15). All had a normal OGTT.