Fetal heart rate patterns in pregnancies complicated by maternal diabetes

Objective: To compare the fetal heart rate (FHR) pattern between fetuses of well controlled diabetic and non diabetic mothers using a computerized analysis of FHR. Study design: Weekly fetal surveillance was performed in 99 fetuses of mothers with diabetes class A, 21 fetuses of mothers with diabetes class B-R, and 55 fetuses of non-diabetic women, starting at 30 weeks' gestation. All diabetic patients were well controlled. Fetal surveillance included a computerized analysis of the FHR, umbilical and uterine Doppler velocimetry, and a biophysical profile. Changes of FHR variation, frequency of FHR accelerations, and umbilical and uterine Doppler velocimetry were calculated using a regression analysis for each patient. The average slopes and the intercept at 30, 34, and 38 weeks' gestation of these variables were compared among the three groups. Results: The slope of FHR variation and the frequency of accelerations had a lower rate of increase during the third trimester in fetuses of mothers with diabetes class A (0.84 ± 0.25 ms/week and 0.06 ± 0.02/20 min/week, respectively) compared with fetuses of non-diabetic mothers (1.34 ± 0.55 ms/week and 0.5 ± 0.1/20 min/week, respectively). In fetuses of mothers with diabetes class B-R, FHR variation did not change with gestation (−0.011 ± 0.2 ms/week) with a small increase in the frequency of accelerations (0.02 ± 0.004/20 min/week. While no differences were observed at 30 weeks' gestation, FHR variation and the frequency of accelerations were significantly reduced at 34 weeks' gestation in fetuses of mothers with diabetes class B-R compared with fetuses of non-diabetic mothers (P < 0.01). At 38 weeks' gestation, fetuses of mothers with diabetes class B-R and diabetes class A had both significantly reduced FHR variation as well as frequency of accelerations compared with fetuses of non-diabetic mothers (P < 0.01). The rate of decrease of the umbilical and uterine artery S/D ratios were similar among the three groups. Conclusions: The FHR pattern appears to be different in fetuses of well controlled diabetic mothers when related to fetuses of non-diabetic mothers. Disease specific standards should be considered for interpretation of FHR patterns in diabetic pregnancies.