Newborns of women who smoked during pregnancy show signs of circulatory dysfunction, according to a novel study from Karolinska Institutet. The findings, which are published in the scientific journal Hypertension, reveal that blood pressure and heart rate control is already abnormal in newborn babies of smoking mothers, and continues to worsen throughout the first year.
The study included 19 infants of non-smoking couples and 17 infants of women who smoked on average 15 cigarettes a day during pregnancy and after their babies were born. The infants in the study were normal weight at birth and breast fed. All infants had blood pressure and heart rates taken while sleeping and tilted up at a 60 degree angle during the first weeks, at three months and one year. They were then lowered back to the supine position.
The blood pressure response to tilting the infants upright during sleep - a test of how the body copes with repositioning - was dramatically different in infants born to smoking mothers compared to those born to non-smoking parents. Infants not exposed to tobacco experienced only a 2 percent increase in blood pressure when they were tilted upright at one week of age and later a 10 percent increase in blood pressure at one year. Infants of smoking mothers had the reverse: a 10 percent increase in blood pressure during a tilt at one week and only a 4 percent increase at one year. At three months and one year, the heart rate response to tilting in the tobacco-exposed infants was abnormal and highly exaggerated, researchers reported.
"Normally when a person stands, the heart rate increases and the blood vessels constrict to keep blood flow to the heart and brain", says Associate Professor Miriam Katz-Salamon. "Our findings show that infants of smokers have a hyper-reactive system in the first weeks of life because the blood pressure increases too much when they are tilted up, but at one year they under-react and are less effective in adapting to an upright position."
The researchers plan to conduct follow-up studies to monitor how the children’s heatlth develops as they grow older.
"Identifying early markers could have broad public health implications, possibly leading to diagnosing, treating and preventing cardiovascular disease earlier", says Miriam Katz-Salamon. "The seeds of many diseases probably are sown very early in life. Babies of smokers may in fact already be showing signs that they are more likely to develop high blood pressure later in life."
Gary Cohen Heather Jeffrey, Hugo Lagercrantz and Miriam Katz-Salamon.Long-term Reprogramming of Cardiovascular Function in Infants of Active Smokers
Hypertension: Journal of the American Heart Association, 25 January 2010