The dynamics of cardiac autonomic control in sleeping preterm neonates exposed in utero to smoking

• Prenatally smoke-exposed neonates have low vagal and elevated sympathetic activities during sleep.
• Maternal smoking during pregnancy disrupts heart rate control dynamics in the neonate.
• The observed effects can be attributed to exclusively prenatal smoking exposure.

Objective: We aimed to determine whether in utero exposure to smoking may influence the activity and dynamics of cardiac autonomic control in preterm infants. We hypothesized that cardiac autonomic control is altered in preterm infants exposed prenatally to smoking and that these effects may vary as a function of the sleep state. Methods: We studied healthy, preterm neonates born to mothers who had smoked throughout pregnancy but not since birth (n = 16). In utero-exposed neonates were matched with control preterm neonates born to non-smoking mothers (n = 18). Cardiac autonomic control was monitored as a function of the sleep state by assessing heart rate variability with both linear and non-linear methods. Results: Preterm neonates with in utero exposure to smoking displayed alterations (relative to control neonates) in short-term cardiac autonomic control in all sleep states. These alterations included low vagal activity, elevated sympathetic activity, and low complexity and adaptability in heart rate control dynamics. Conclusions: Our results constitute direct evidence that cardiac autonomic activity and control are altered in sleeping preterm infants exposed to smoking in utero. Significance: These alterations may place the affected infants at a higher risk of neurological and cardiovascular complications, which could conceivably persist throughout childhood and adulthood.