Fetal growth restriction: From Polyvagal theory to developmental impairments?

Abstract Background The Polyvagal theory argues that behavioral modulation is a fundamental neurodevelopmental process that depends on autonomic regulation. Objective The present study aimed to assess sleep architecture in newborns with fetal growth restriction (FGR) using polysomnography as an indicator of Polyvagal theory. Methods We studied polysomnography recordings from 68 preterm infants, 34 with FGR and 34 born with appropriate growth for gestational age (AGA), who were matched according to the corrected age for prematurity (CA). Total sleep time, arousals, the percentage of quiet sleep, active sleep, indeterminate sleep, and heart rate were compared between the groups. Linear multiple regression analyses were used to evaluate polysomnography data for the FGR and AGA groups. Results Average heart rate was significantly lower in most FGR groups compared with AGA groups, and small to large effect sizes were observed in several sleep responses when comparing these groups. In the lineal regression model the CA explains significantly the differences in heart rate, controlled by FGR (p = .012). Additionally, there was evidence that sleeping states show similar trends, that is, increases in quiet and indeterminate sleep, as well as decreases in active sleep when CA was controlled by FGR. Conclusion FGR probably intensifies the unfavorable effect of preterm birth in the responses evaluated by polysomnography. It seems that FGR is associated with alteration in sleep regulation and with differences in heart rate modulation, which may serve as a strategy to preserve energy and such differences likely underlie neurodevelopmental impairments in affected newborns.