Background In premature infants, we investigated whether the duration of extrauterine development influenced autonomic nervous system (ANS) maturation. Methods We performed a longitudinal cohort study of ANS maturation in preterm infants. Eligibility included birth gestational age (GA) < 37 weeks, NICU admission, and expected survival. The cohort was divided into three birth GA groups: Group 1 (≤29 weeks), Group 2 (30–33 weeks), and Group 3 (≥34 weeks). ECG data were recorded weekly and analyzed for sympathetic and parasympathetic tone using heart rate variability (HRV). Quantile regression modeled the slope of ANS maturation among the groups by postnatal age to term-equivalent age (TEA) (≥37 weeks). Results One hundred infants, median (Q1−Q3) birth GA of 31.9 (28.7–33.9) weeks, were enrolled: Group 1 ( n = 35); Group 2 ( n = 40); and Group 3 ( n = 25). Earlier birth GA was associated with lower sympathetic and parasympathetic tone. However, the rate of autonomic maturation was similar, and at TEA there was no difference in HRV metrics across the three groups. The majority of infants (91%) did not experience significant neonatal morbidities. Conclusion Premature infants with low prematurity-related systemic morbidity have maturational trajectories of ANS development that are comparable across a wide range of ex-utero durations regardless of birth GA. Impact Heart rate variability can evaluate the maturation of the autonomic nervous system. Metrics of both the sympathetic and parasympathetic nervous system show maturation in the premature extrauterine milieu. The autonomic nervous system in preterm infants shows comparable maturation across a wide range of birth gestational ages. Preterm newborns with low medical morbidity have maturation of their autonomic nervous system while in the NICU. Modern NICU advances appear to support autonomic development in the preterm infant.

Fetal growth restriction (FGR) impairs the pulmonary development and increases the risk for neonatal respiratory morbidity. There is urgent need to identify prenatally those growth restricted infants at highest risk for respiratory complications at birth. We aimed to evaluate the role of fetal pulmonary vasoreactivity (PVRO2) in identifying newborns at risk for respiratory morbidities among pregnancies complicated by FGR. Singleton pregnancies with FGR (estimated fetal weight < 10th and/or abdominal circumference < 5th percentile) without congenital abnormalities, infections, genetic syndromes, maternal chronic respiratory morbidity, use of tobacco, alcohol or recreational drugs, underwent maternal hyperoxia (MH) every two weeks, from enrollment to delivery. The pulsatility index (PI) of the middle branch of the pulmonary arteries (mPA) was obtained by ultrasound at baseline, during MH and after 15 minutes of maternal administration of 8 L/min of 100% oxygen through a non-rebreathing face mask. A reactive PVRO2 test was defined as any decrease in mPA-PI during MH compared to baseline. Newborns were divided in two groups based on need for respiratory support at delivery and/or admission to the neonatal intensive care unit due to respiratory morbidities (Group 1) or absence of need for respiratory support at birth (Group 2). Results of the last PVRO2 test prior to delivery were compared with neonatal outcomes. Among 13 subjects, 10 participants were eligible for analysis (Group 1=5; Group 2=5) (Tables 1). Among Group 1, three fetuses had a non-reactive PVRO2 test, while all fetuses in Group 2 had a reactive test. Sensitivity, specificity, positive (PPV) and negative predictive (NPV) values were respectively 60%, 100%, 100% and 71.4%. Comparison of the two groups is presented in Table 2. PVRO2 tested by MH is a non-invasive test with 100% specificity and 100% PPV in prenatally identifying those newborns at highest risk for respiratory morbidities at birth, among pregnancies complicated by fetal growth restriction. Our results need to be confirmed in a larger population.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Delivery of the newborn occurs either vaginally or via caesarean section. It is not known whether the mode of delivery and exposure to labor affects early autonomic nervous system (ANS) function, as measured by heart rate variability (HRV), or cortical electroencephalogram (EEG) activity. The objective of the study was to determine if autonomic function in newborns differs by mode of delivery. Simultaneous recording of EEG and electrocardiogram were collected in low-risk term newborns at <72 hours of age to measure HRV, the asymmetry index, and EEG power. Newborns were compared by delivery type: vaginal delivery (VD), cesarean section (CS) after labor (L-CS), or elective CS (E-CS). Quantile Regression controlled for gestational age, postnatal age, and percent active states. One hundred and eighteen newborns were studied at 25.2 (11.4) hours of age. Sixty-two (52.5%) were born by VD, 22 by L-CS (18.6%), and 34 by E-CS (28.8%). HRV metrics didn't differ by delivery mode. Asymmetry index was higher in L-CS compared to VD and E-CS (P = 0.03). On EEG, L-CS newborns showed lower relative gamma power compared to VD and E-CS (P = 0.005). The study found that overall ANS tone is not altered by mode of delivery in low-risk term newborns.