Correlation between amniotic fluid glucose concentration and amniotic fluid volume in pregnancy complicated by diabetes

OBJECTIVE: Pregnancies complicated by diabetes are frequently characterized by an increased Volume of amniotic fluid, and the pathophysiologic mechani sm of this increase is not known. Our goal was to evaluate the relationship between amniotic fluid glucose concentration and the amniotic fluid index in pregnancies complicated by insulin-treated diabetes and to compare it wi th that seen in normal pregnancies. STUDY DESIGN: Amniotic fluid index and amniotic fluid glucose levers were m easured before elective repeated cesarean delivery in 41 women with insulin -treated diabetes and in 35 women without diabetes. Only singleton gestatio ns without anomalous fetuses were included. Women with diabetes were hospit alized for approximately 4 weeks before delivery, during which time glycemi c control was optimized. Amniotic fluid index and amniotic fluid glucose co ncentration were correlated with each other and were compared between the g roups with and without diabetes. RESULTS: The mean amniotic fluid index was significantly increased in the d iabetes group (16.6 +/- 5.0 cm in the diabetes group vs 13.4 +/- 3.5 cm in the control group; P = .002). The amniotic fluid glucose concentration was also significantly greater in the diabetes group than in the control group (39 +/- 17 mg/dL in the diabetes group vs 24 +/- 11 mg/dL in the control gr oup; P < .001). Among women with diabetes the amniotic fluid glucose concen tration was significantly correlated with the amniotic fluid index (r = 0.3 2; P = .04), a correlation not found among the control women. The mean fast ing blood glucose concentration among the women with diabetes for the week before amniocentesis was 82 +/- 11 mg/dL. CONCLUSION: The amniotic fluid index parallels the amniotic fluid glucose l evel among women with diabetes. This finding raises the possibility that th e hydramnios associated with diabetes is a result of increased amniotic flu id glucose concentration.