(RxWiki News) Expectant mothers should be wary of second-hand smoke. Exposure to second-hand smoke has been shown to increase the risk of asthma and wheezing in children.
In a new study, researchers examined 79 studies involving second-hand smoke and its effects on children from the prenatal stages of life to infancy.
The studies were observational and focused on the effects of second-hand smoke exposure during pregnancy, after pregnancy and in the household on children up to the age of 18.
They continued to show that second-hand smoke exposure increased the risk of asthma and wheeze in children by up to 70 percent in some cases.
"Ask your doctor about risk factors during pregnancy. "
The study was led by Hannah Burke, BMBS, Division of Epidemiology and Public Health, University of Nottingham, City Hospital. Rather than conduct another study involving second-hand smoke exposure, researchers examined all the previous studies to determine how great of a risk second-hand smoke exposure was to the development of childhood wheeze and asthma.
The 79 studies were cohort based, which involved observing groups of individuals to determine the effect of a potential risk factor.
For children under the age of two, maternal smoking during the prenatal stage of pregnancy was associated with a 40 percent increase in the risk of childhood wheeze based on 14 studies. For children the age of five to 18, the risk of childhood wheeze was increased by 52 percent, based on five studies.
Children exposed to smoke after pregnancy had the greatest risk increase of childhood wheeze for children under the age of five.
Children under the age of two exposed to second-hand smoke in the household had their risk of childhood wheeze increased but there was no significant association for children aged three to four.
Mothers who smoked during pregnancy increased the risk of children under the age of two developing asthma by 85 percent, according to five studies. The risk of asthma development due to prenatal smoking decreased as a child grew up, but smoking during pregnancy was still strongly associated with asthma development in children, based on 11 studies.
Overall, second-hand smoke exposure increased the risk of developing childhood wheeze or asthma by at least 20 percent, according to the researchers.
Naturally, this risk may increase or decrease based on the levels of exposure. Other factors, such as maternal asthma, can also increase the risk of developing childhood respiratory disease.
The study was published in the April edition of Pediatrics.
Funding for the study was provided by Cancer Research UK and the British Heart Foundation, Cancer Research UK, Economic and Social Research Council, Medical Research Council, and the Department of Health.