BACKGROUND to study the relation between amniotic fluid volume and glycemic control in pregnancies complicated by diabetes mellitus type 1 and 2, followed in a specialized multidisciplinary prenatal care service. METHODS This descriptive study was performed between January 2001 and December 2004. Inclusion criteria were: simple pregnancy, diagnosis of pregestational diabetes, beginning of prenatal care before the 26th week and absence of fetal anomaly. Cases with newborns small for gestational age were excluded. The amniotic fluid index (AFI) was measured weekly, beginning at the 27th week of gestation and continued until delivery and the maternal glycemic profile was obtained a week before ultrasound assessment. This profile consisted of the glycemic level averages and percentages of the abnormal high values. Correlation between the glycemic profile and the AFI was shown by the Spearman correlation test. RESULTS Sixty pregnant women were assessed and 659 correlations between the AFI and glycemic profile were obtained. No correlation was observed in any of the gestational weeks studied. The mean glycemic value was 103.69 mg/dl (SD=13.69) in the group with AFI pound18 cm, and the 103.67 mg/dl (SD=11.46) in the group with AFI < 18 cm and no significant difference was detected. CONCLUSIONS This study showed no correlation between AFI and maternal glycemic profile during the third trimester in type 1 and 2 diabetic pregnant women, undergoing standardized treatment and rigorous metabolic control.