Effects of maternal glycemia on fetal heart rate in pregnancies complicated by pregestational diabetes mellitus.

Objective: To investigate the influence of maternal glycemia on fetal heart rate (FHR) parameters analyzed by computerized cardiotocography in fetuses of diabetic mothers in the third trimester.

Study Design: Thirty-nine pregnant women with pregestational diabetes mellitus were studied prospectively. The inclusion criteria were a diagnosis of pregestational diabetes, singleton pregnancy between 36 and 40 weeks, and absence of fetal abnormalities. Computerized cardiotocography (System 8002) was performed over a period of 60 min and capillary glycemia was measured immediately before and 30 and 60 min after the beginning of the exam. The evaluations were done 2 h after lunch.

Results: Nineteen patients (48.7%) presented mean glycemia > or =120 mg/dL. The mean basal FHR was 136.7+/-10.0 bpm in the group with glycemia <120 mg/dL and 144.8+/-9.4 bpm in the group with glycemia > or =120 mg/dL (p=0.013, Student's t test). There was a significant positive correlation (Pearson's test, p=0.0001, r=0.57) between basal FHR and mean glycemia. A significant negative correlation was observed between short-term variation and mean glycemia (Pearson's test, p=0.003, r=-0.47). No significant differences were observed between the other indices evaluated by computerized cardiotocography and glycemia.

Conclusions: Maternal hyperglycemia at the time of cardiotocography is associated with elevated FHR. It seems to be important to understand how FHR parameters are influenced by maternal glycemic status at the time of fetal assessment in pregnancies complicated by diabetes.