Maternal Cardiac Autonomic Function and Fetal Behaviour in Hypertensive and Obese Pregnancies
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Hypertension in pregnancy is associated with autonomic dysregulation whereas the effects of obesity in pregnancy on maternal cardiac autonomic function are poorly understood. Furthermore, hypertension in pregnancy is associated with placental insufficiency and fetal growth restriction, whereas obesity in pregnancy is associated with placental inflammation and macrosomia. Fetal growth restriction is associated with an increased risk for language deficits at 2-5 years of age. However, maternal cardiac autonomic function and fetal auditory processing in pregnancies complicated by hypertension compared to obesity have not been examined and are the focus of this study. Maternal short-term cardiac autonomic modulation in the supine and standing postures as well as spontaneous and auditory elicited fetal behaviours were compared in 61 mother-fetal pairs (n=20 hypertensive; n=20 overweight; n=21 normal weight comparison pregnancies) from 34 to 40 weeks gestation. Maternal cardiovascular measures included systolic arterial finger-cuff blood pressure and electrocardiographic recordings of heart rate. Spontaneous observations of fetal heart rate, body and breathing movements, muscle tone and an estimate of amniotic fluid were made. Finally, each fetus received a 2 min recording of their mother and the mother’s voice in reverse (counterbalanced over subjects). When standing (othostatic stress), all three groups of women exhibited a decrease in the average baroreflex slope, parasympathetic nervous system indicator and high frequency power compared to the supine position. In a 20 min observation of spontaneous behaviour in the maternal supine compared to the standing position, fetuses of hypertensive mothers had, on average, fewer heart rate accelerations ≥ 15 bpm while the mother was supine; fetuses in the normal weight comparison group experienced more accelerations while the mother was supine. The average number of heart rate accelerations did not change in the two maternal positions for fetuses in the obese group. Fetuses in the three groups showed differential responses to the mother’s voice played forward and backward. It was concluded that there were no differences in maternal heart rate variability measures in the group of mildly hypertensive women compared to those with obesity and the normal weight comparison group. Differential spontaneous fetal heart rate accelerations and responses to the mother’s voice among the three groups needs further study with sufficient sample size to examine behaviour as a function of gestational age.