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Baby's blood pressure damaged by smoking during pregnancy
Swedish research has found that babies whose mothers smoked during pregnancy have unusual surges in their blood pressure during the first year of their life. These surges of high blood pressure make the heart beat harder and faster, putting extra strain on the heart and blood vessels.
Since these surges can happen at night, when the baby is sleeping peacefully in its cot, the researchers suggest that these blood pressure surges could be responsible for some cot deaths.
It is well known that smoking during pregnancy is one of the most important risk factors for causing cot death - also known as sudden infant death syndrome (SIDS). The research, published in the January issue of the journal Hypertension, offers a possible explanation of how a mother's smoking can increase a baby's risk.
The researchers, from the Karolinksa Insitute in Sweden, looked at the blood pressures of 36 newborn babies over their first year of life. They compared the blood pressure responses of the 19 babies whose mothers who didn't smoke with the 17 babies whose mothers did.
The differences in blood pressure control between the babies was apparent even in the first week of life. When the babies were lifted up from lying down, the babies of smoking mothers had unusually high blood pressure surges when compared with babies of nonsmoking mothers.
Normally a person's blood pressure rises slightly when standing up from sitting or lying down, to work against the effects of gravity and keep the blood flowing normally to the brain. In the babies of smoking mums, this rise was too high.
The abnormal blood pressure and heart rate changes became worse over the course of the first year. By the end of the first year, the babies of smoking mothers had adapted to the unusually high blood pressure surge by developing unusually low blood pressure rises when being lifted up from lying down. This suggests that they could struggle to keep up a strong blood pressure flow to the brain at the moment of being lifted up.
The researchers are hoping to continue to follow the babies as they grow up to see if this blood pressure problem continues and whether it leads to long-term high blood pressure in later life.
The current advice from medical experts is to avoid exposing babies - both born and unborn - to smoke of any kind. Both mothers and fathers are encouraged to avoid smoking during the pregnancy and to prevent anyone from smoking in the same room as their baby.
Gary Cohen, Heather Jeffery, Hugo Lagercrantz, and Miriam Katz-Salamon. Long-Term Reprogramming of Cardiovascular Function in Infants of Active Smokers. Hypertension, Jan 2010; doi:10.1161/HYPERTENSIONAHA.109.142695
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