UWC research has found that for every one-unit increase in adolescent BMI systolic blood pressure increased by 1.38 mmHg - a risk factor for elevated blood pressure later in life. Image:Marta Branco/Pexels

Children exposed to tobacco smoking in the womb face a higher risk of developing high blood pressure during adolescence, with body weight emerging as a key factor that is linked to elevated blood pressure, new University of the Western Cape (UWC) research suggests.

The study that was conducted among 307 adolescents aged 10 to 14 from Bishop Lavis in Cape Town, examined how exposure to cigarette smoking and alcohol during pregnancy could influence cardiometabolic risk factors later in life. Cardiometabolic risk refers to the chances of developing diseases related to both the heart and metabolism, such as high blood pressure, obesity, diabetes, heart disease and stroke.

After measuring the children’s height, weight, blood pressure and cholesterol levels to investigate links between prenatal exposure and later health outcomes, researchers found that maternal smoking had a significant direct effect on adolescent systolic blood pressure (SBP), and an indirect effect through Body Mass Index (BMI). 

New findings show that male adolescents exposed to smoking in the womb were likely to have low HDL cholesterol - the good cholesterol which helps protect against a heart attack and stroke. Image:Towfiqu barbhuiya/Pexels

For every one-unit increase in BMI - a measure used to determine whether a person’s weight is healthy for their height - SBP increased by 1.38 mmHg. This suggests these children may face a greater risk of developing elevated blood pressure later in life.

Systolic blood pressure - the top number in a blood pressure reading - is important in one’s overall health because it measures the pressure in arteries pumped by the heart. If it’s consistently elevated it is considered a concern because it places extra strain on the heart and blood vessels over time.

Researchers also reported that male adolescents exposed to smoking in the womb were six times more likely to have low HDL cholesterol - the good cholesterol which helps protect against a heart attack and stroke.

Published in the Journal of Public Health, the study was led by Dr Tammy Ras, a lecturer in the Department of Medical Bioscience, and co-authored by her PhD supervisors Dr Juléy De Smidt and Prof André Oelofse. The researchers found that children born to mothers who smoked during pregnancy were generally smaller at birth, supporting previous research linking smoking to low birthweight.

Dr Tammy Ras, a lecturer in the Department of Medical Bioscience and a lead researcher. Image: Supplied

While birth weight did not affect adolescents becoming overweight or elevate their blood pressure, BMI was the main driver linking maternal smoking during pregnancy to later risks such as high blood pressure, excess weight and obesity.

Researchers suggest the lower risk of excess weight during adolescence may be linked to babies exposed to cigarette smoke in the womb being born smaller and remaining smaller throughout childhood, possibly due to poverty and food insecurity.

However, among adolescents exposed to both cigarette smoke and alcohol in the womb, girls, notably, had higher BMI levels and greater body fat measurements than boys, suggesting higher levels of body fat accumulation in girls at this age.

In conclusion, the authors suggested that girls exposed to cigarette smoking and alcohol in the womb, regardless of whether they were born underweight or overweight, could reduce their risk of future heart and metabolic diseases by maintaining a healthy weight. They suggested ongoing monitoring is important, as obesity and high blood pressure during adolescence often persisted into adulthood.

“Prospective research studies in the field are needed in low socioeconomic populations to further investigate the effects of teratogens (any substances, organisms, physical agents or states which can disrupt healthy fetal development and cause dangerous complications) on cardiometabolic risk factors in adolescents. This is critical as more than 60% of women smoke cigarettes, drink alcohol or both during their pregnancy, as reported in previous South African studies,” the researchers said in the study.