Maternal cigarette smoking and prenatal nicotine exposure increase the risk for sudden infant death syndrome (S1DS) by 2-to 4-fold,yet despite adverse publicity,nearly one of four pregnant women smoke tobacco in USA.Infants who succumb to SIDS typically experience a severe bradycardia that precedes or is accompanied by centrally mediated life-threatening apneas and gasping.Although the causes of the apnea and bradycardia prevalent in SIDS victims are unknown,it has been hypothesized that these fatal events are exaggerated cardiorespiratory responses to hypoxia or hypercapnia.Changes in heart rate are primarily determined by the activity of cardiac vagal neurons (CVNs) in the brainstem.