Aims of the study were: evaluation of HbA1c levels in the peripheral blood of pregnant women with insulin dependent diabetes, gestational diabetes, glucose intolerance, and healthy pregnant controls; implications of HbA1c concentration on detection and the control of women with impaired carbohydrate metabolism in pregnancy; comparison of HbA1c levels with appearance of miscarriages, and premature deliveries; comparison of weight gain during pregnancy to HbA1c levels; comparison of difference from ideal body weight with HbA1c in diabetic pregnant women; comparison of neonatal birth weight and HbA1c levels. 290 pregnant women were enrolled to the study. The highest value of HbA1c was in the group IDDM pregnant women (7.7% +/- 1.8%), and the lowest value of HbA1c was in the control group (4.1% +/- 0.5%). Statistically significant coefficients were found between HbA1c and weight gain during pregnancy, between weight deviation from ideal body weight and HbA1c (r = 0.54 and r = 0.48 respectively); and between newborns weight and HbA1c (r = 0.51). Well regulated glycemia and intensive pregnancy follow-up of diabetic women reduces stillbirths, neonatal complications and neonatal macrosomia incidence.