Long-term reprogramming of cardiovascular function in infants of active smokers.

Newborn infants of smokers show symptoms of cardiovascular stress hyperreactivity. Persistent hyperreactivity could increase the risk of short- and/or long-term complications, such as hypertension. Here we determined whether incipient dysfunction in a smoker's infant persists or worsens with age, by comparing cardiovascular reflex function of control and tobacco-exposed infants longitudinally from birth to 1 year. We compared infants born at term to nonsmoking couples (controls; n=19) and mothers who smoked moderately (average consumption=15 cigarettes per day; n=17). All were tested at 1 to 3 weeks, 3 months, and 1 year during sleep. We recorded blood pressure and heart rate noninvasively during passive repositioning (60 degrees head-up tilt). Tilting control infants raised blood pressure slightly above baseline at 1 week (+2%) and much more at 1 year (+10%). This trend was reversed in the tobacco-exposed cohort (+10% at 1 week but only +4% at 1 year). At 3 months and 1 year, the heart rate response of tobacco-exposed infants to tilt was also abnormal (highly exaggerated). Our study reveals that maternal smoking leads to long-lasting "reprogramming" of infant blood pressure control mechanisms. The underlying dysfunction in a smoker's infant could plausibly be a precursor or early marker of long-term susceptibility to complications, such as raised blood pressure.