A new study published in the American Journal of Respiratory and Critical Care Medicine shows a causal link between smoking during pregnancy and sudden infant death syndrome (SIDS).
Clinicians have long considered prenatal cigarette smoke exposure a major contributing risk factor for SIDS, but researchers had not proved a casual relationship.
"Our results provide some of the most direct evidence to date suggesting that prenatal cigarette smoke exposure can contribute to the destabilising effects of hypoxia and thermal stress on neonatal breathing," said Dr Shabih Hasan, staff neonatologist and associate professor in the department of pediatrics at the University of Calgary
"Our approach sought to quantify the effects of cigarette smoke holistically, rather than using nicotine exposure as a proxy for cigarette smoke. Nicotine is just one of the 4,700 known toxins in cigarette smoke that could have protracted effects on embryonic development and postnatal growth.
"Our results show that prenatal cigarette smoke exposure compounds the risk by increasing the likelihood of gasp-like respiration and prolonging the time that it takes for neonates to return to normal breathing following hypoxia.
"These observations provide important evidence of how prenatal cigarette smoke exposure, hypoxic episodes and hyperthermia might place infants at higher risk for SIDS and further support efforts to foster prenatal smoking cessation programs," said Dr Hasan.
Other contributing factors include disturbances of breathing and heart rate regulation and impaired arousal responses, thermal stress (primarily overheating from too high temperatures or too much clothing) and sleeping in the prone (belly-down) position.