Dummy/pacifier use is protective for sudden infant death syndrome (SIDS); however, the mechanism/s for this are unknown. As impaired cardiovascular control may be the underlying cause of SIDS, we assessed the effects of dummy/pacifier use on cardiovascular control during sleep within the first 6 months of life. METHODS: Term infants, divided into dummy/pacifier users and non-dummy/pacifier users, were studied at 2-4 weeks (n = 27), 2-3 months (n = 35) and 5-6 months (n = 31) using daytime polysomnography. Heart rate, blood pressure (BP), heart rate variability (HRV), blood pressure variability (BPV), and baroreflex sensitivity (BRS) were measured in triplicate 1-2-min epochs during quiet and active sleep in the supine and prone positions. RESULTS: Overall, during the non-sucking periods, in the prone position, the BP was higher (10-22 mmHg) in dummy/pacifier users compared to non-users at 2-4 weeks and 5-6 months (p <0.05 for both). HRV and BRS were higher in dummy/pacifier users compared to non-users at 2-4 weeks (p <0.05). Active sucking increased HRV and BPV, consistent with increased sympathetic activity in dummy/pacifier users. CONCLUSIONS: Higher BP and HRV in dummy/pacifier users indicate increased sympathetic tone, which may serve as a protective mechanism against possible hypotension leading to SIDS; however, these effects were not apparent at 2-3 months, when the risk of SIDS is highest.