A new study by researchers at McMaster University USA, published online in the journal Federation of American Societies for Experimental Biology (FASEB) to be available in the May 2008 print issue, has shed some light on the relationship between women who smoke while pregnant, or are exposed to second-hand smoke, and an increased risk of Sudden Infant Death Syndrome (SIDS) to their babies.
Researchers found out that a specific mechanism is the reason a baby's ability to respond to oxygen deprivation after bith (called a hypoxic episode) is significantly reduced if they are exposed to even light to moderate amounts of nicotine in the womb.
"While cigarette smoke contains many different compounds, we found there is a direct impact of one component, nicotine, on the ability of certain cells to detect and respond to oxygen deprivation," says Josef Buttigieg, lead author and a PhD student in the Department of Biology. "When a baby is lying face down in bed, for example, it should sense a reduction in oxygen and move its head. But this arousal mechanism doesn't work as it should in babies exposed to nicotine during pregnancy."
The research explains the role that specific hormones from the adrenal glands - catecholamines - play in a baby's transition outside the womb and especially it's ability to breath properly.
During the birth, the baby is exposed to low oxygen, which tells the adrenal glads to release the catecholamines (that contain adrenaline), explains Buttigieg.
It is the catecholamines that instruct the baby's lungs to reabsorb fluid, to take its first breath and help the heart beat more efficiently. The adrenal glands still act as an oxygen sensor, for some months after birth, which helps the baby's arousal and breathing responses during periods of apnoea or asphyxia.
The baby's ability to release catecholamines during periods of apnoea or asphyxia (very critical to the baby's ability to survive outside the womb) is very impaired due to the baby's exposure to nicotine while in the womb.
"At birth, the nervous control of the adrenal gland is not active and so a baby relies on these direct oxygen sensing mechanisms to release catecholamines," says Colin Nurse, academic advisor on the study and a professor in the Department of Biology. "But nicotine causes premature loss of these mechanisms, which would normally occur later in development after nervous control is established. Thus, the infant becomes much more vulnerable to SIDS."
The study was funded in part by the Heart & Stroke Foundation of Ontario, Canadian Institutes of Health Research and Focus on Stroke.
McMaster University Press Release - 29 January 2008
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