Smoking during Pregnancy May Up Sudden Infant Death Syndrome Risk

Tobacco smoking during pregnancy may put your developing fetus at a higher risk of sudden infant death syndrome (SIDS) and cardiac arrhythmias. Hence, prolonged exposure to nicotine while in the womb can cause sudden unexpected death in babies.

Pregnant mothers who smoke tobacco often put their developing fetus at a higher risk of sudden infant death syndrome (SIDS), reports a new study. The findings of the study are reported in HeartRhythm, the official journal of the Heart Rhythm Society and the Cardiac Electrophysiology Society, published by Elsevier.//

Fetal exposure to tobacco smoke in utero is associated with sudden infant death syndrome (SIDS) and cardiac arrhythmias in newborns. In a novel study in rabbits, investigators provide the first evidence linking fetal exposure to nicotine to long-term alterations of the cardiac sodium current. These changes may impair adaptation of the cardiac sodium current to sympathetic tone and prevent awakening from sleep apnea, leading to arrhythmias that could potentially be involved in SIDS.

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‘Moms who smoke during pregnancy are more likely to increase the unborn child's risk of sudden infant death syndrome (SIDS) and cardiac arrhythmias.’
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SIDS, or crib death, is the leading cause of death in the first year of life. In utero exposure to tobacco smoke remains the highest risk factor in 85 percent of cases. It, therefore, seems logical to prescribe nicotine replacement therapies (NRTs) to pregnant women who wish to quit smoking. Tobacco smoke contains over 3,000 toxic compounds identified so far, but out of all the toxic compounds found in smoke, only nicotine is associated with cardiac arrhythmias in newborns.

"Clinicians often prescribe NRTs to pregnant women who wish to quit smoking in order to reduce the number of crib deaths," explained lead investigator Robert Dumaine, Ph.D., Department of Pharmacology and Physiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, QC, Canada. "However, our data show that nicotine alone is sufficient to alter electrical currents within the heart and generate arrhythmias leading to crib death."

In the womb, the fetus cannot breathe on its own, and its heart reacts to a reduction in oxygen by slowing the beating rate and its metabolism to preserve energy. This fetal adaptation is known as 'diver reflex.'

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On the other hand, when an infant suffocates during sleep, the brain senses the reduction of oxygen in the blood and will trigger the secretion of adrenalin (epinephrine) to accelerate heart rhythm. Once cardiac rhythm accelerates, in part due to increased excitability (sodium current) in the heart, the baby wakes up. This "resuscitation reflex" seems to be absent in babies with SIDS. Instead, those infants display a slowing of heart rate when lacking oxygen, as if their postnatal cardiac development had been delayed and still in a fetal state.

"The importance of this study is that, for the first time, we provide direct evidence that in utero exposure to nicotine has postnatal effects on the development of the heart and its response to adrenalin and may provide a basis to explain why some babies do not wake up during sleep apnea," commented Dr. Dumaine. "Therefore, it might be worthwhile to revisit the clinical practice of prescribing the nicotine patch and other NRTs to pregnant women."