Healthy prepubescent children with mothers who smoked during pregnancy have lower levels of high density lipoprotein (HDL) cholesterol compared with children born to women who do not smoke during pregnancy, Dr. Julian G. Ayer of the University of Sydney, and his colleagues, reported in a longitudinal study published June 21 in the European Heart Journal.
Previous studies have shown an association between environmental tobacco smoke (ETS) exposure in adults and cardiovascular disease (CVD) and an increase of the thickening of the arterial wall and lipid alternations associated with atherosclerosis. Thus, Dr. Ayer and associates decided to examine the effects of maternal smoking in pregnancy on the lipoprotein levels and arterial wall thickness in 8-year-old children and to determine whether smoking during pregnancy could increase the risk of CVD in children later in life (Eur. Heart J. 2011 June 21 [doi:10.1093/eurheartj/ehr174]).
Photo credit: Catherine Harrell
Children born to mothers who smoked while pregnant should be watched for coronary risk factors, such as high blood pressure, high LDL, ‘bad’ cholesterol levels, and cigarette smoking themselves later in life, researchers said.
"Cholesterol levels tend to track from childhood to adulthood, and studies have shown that for every 0.025-mmol/L increase in HDL levels, there is an approximately 2%-3% reduction in the risk of coronary heart disease," Dr. David Celermajer, Scandrett Professor of Cardiology at the university, who led the study, said in a written statement. "If we extrapolate this, we can suggest that the difference of 0.15 mmol/L between children of smoking mothers versus nonsmoking mothers might result in a 10%-15% higher risk for coronary disease in the children of smoking mothers. This is an approximation only, but the best one we have."
Results showed that children born to mothers who smoked during pregnancy had lower HDL cholesterol (1.32 vs. 1.50 mmol/L), higher triglycerides (1.36 vs.1.20 mmol/L) and higher systolic blood pressure (102.1 vs. 99.9 mm Hg). When postnatal ETS exposure and other confounders such as breastfeeding duration, physical inactivity, and maternal exposure to passive smoking during pregnancy were factored into the study, the children still had lower HDL cholesterol, (difference of -0.22 mmol/L) but had no significant difference in systolic blood pressure. When excluding postnatal ETS exposure and including all other confounders, the difference was about -0.14 mmol/L. There was no significant difference in carotid intima-media thickness (CIMT) due to smoking in pregnancy or postnatal ETS exposure.
The participants in the study included 616 newborns from Sydney who were enrolled into the Childhood Asthma Prevention Study (CAPS), a randomized controlled trial investigating for asthma and allergic disease in children from birth to 5 years of age between September 1997 and December 1999. At 8 years of age, 405 of the 616 children (66%) had parental consent to participate in a cardiovascular substudy that examined the effect of the dietary intervention on CVD risk factors. Three hundred twenty-eight children (53%) had permission to participate in the lipoprotein examination.
Using a questionnaire at an in-person interview, mothers were asked about their smoking habits during all three trimesters of their pregnancy as "1-10/day," "11-20/day," "20-40/day,’ or "greater than or equal to 41/day." The smoking average was then calculated during midpoint values for each range (5, 15, 30, and 50, respectively). Mothers also were asked whether anybody else in the home smoked during pregnancy.
Information on postnatal ETS exposure was collected during visits to the home or by telephone at the age of 4 weeks, at 3 monthly intervals from the age of 3 months to 5 years, and at six monthly intervals to the age of 7.5 years.
Dr. Ayer and associates reported that results may be important in the prevention of atherosclerosis as about 15% of women in Western countries smoke during pregnancy.
"Children born to mothers who have smoked during pregnancy will need to be watched particularly carefully for other coronary risk factors, like high blood pressure, high LDL, ‘bad’ cholesterol levels, and especially cigarette smoking themselves," Dr. Celermajer said in the statement.
He suggested that HDL levels can be increased with frequent physical activity and medications such as niacin.
Researchers received funding from an Australian Government National Health and Medical Research Council Project Grant and a Pfizer CVL Grant. Funding was also provided by the National Health and Medical Research Council of Australia; Cooperative Research Centre for Asthma, New South Wales; Department of Health; and Children’s Hospital at Westmead. The researchers reported no relevant financial disclosures.