Introduction: Sighs (deep inspirations) are thought to have an important role in restoring lung volume, resetting the mechanical properties of lung tissue and in resetting neurorespiratory control. In quiet or non-rapid eye movement sleep, sighs are often followed by post sigh central apnea. Sighs reduce in frequency with maturation over the first year of life. We speculate that cardiorespiratory synchronization (CRS), as a measure of neurorespiratory control, would differ between sigh with and without central apnea, and change with maturation. We also hypothesize that infants with chronic neonatal lung disease (CNLD) would display differences in CRS preceding sigh versus measurements derived from healthy infants.Methodology: Full overnight polysomnography (PSG) data was obtained from prospective cohorts of 34 healthy infants (aged 2 weeks, 3 months and 6 months old) and of 82 CNLD infants (aged 3-6 months old). Both groups were studied in room air. CRS strength was assessed by a phase synchronization method measuring coupling between breathing and heart beat obtained from the R-wave. The synchronization index varies from 0 (unsynchronized) to 1 (perfectly synchronized). Results: Our results show a significant decrease of CRS prior to sigh followed by a post sigh central apnea (sigh-PSCA) compared to sigh alone in both healthy and CNLD infants. In the healthy infant group, CRS index was lower with sigh-PSCA (0.59, 0.68, 0.69) at 2 weeks, 3 months and 6 months of age, respectively) than with sigh alone (0.65, 0.72, 0.79, respectively). In the CNLD group, CRS index was also lower with sigh-PSCA (0.66) than with sigh alone (0.71). Using healthy infant’s data at 2 weeks old as reference, CRS increased at 3 months of age and further increased at 6 months of age. The greatest change was observed between 2 weeks and 3 months of age.Conclusion: CRS changes with infant maturation. Post sigh central apnea is associated with a significant decrease in CRS preceding the apneic event.