Children exposed to cigarette smoke in the womb are at greater risk of developing high blood pressure during adolescence — and body weight plays a major role, new research from the University of the Western Cape (UWC) has found.

Bishop Lavis

The study, conducted among 307 young people aged 10 to 14 from Bishop Lavis in Cape Town, looked at how exposure to smoking and alcohol during pregnancy could affect a child’s health years down the line. Researchers measured the children’s height, weight, blood pressure and cholesterol levels to investigate links between what they were exposed to before birth and their health as adolescents.

Maternal smoking had a significant effect on adolescent systolic blood pressure — the top number in a blood pressure reading, which measures the pressure in the arteries when the heart beats. If consistently elevated, it places extra strain on the heart and blood vessels over time.

Researchers found that for every one-unit increase in Body Mass Index (BMI) — the measure used to determine whether a person’s weight is healthy for their height — systolic blood pressure increased by 1.38 mmHg. This suggests these children may face a greater risk of high blood pressure as they get older. Male adolescents exposed to smoking in the womb were also found to be six times more likely to have low HDL cholesterol — the so-called “good” cholesterol that helps protect against heart attacks and strokes.

Journal of Public Health

The study was published in the Journal of Public Health and was led by Dr Tammy Ras, a lecturer in the Department of Medical Biosciences at UWC, together with her PhD supervisors Dr Juléy De Smidt and Prof André Oelofse.

Children born to mothers who smoked during pregnancy were generally smaller at birth — supporting earlier research linking smoking to low birthweight. While birthweight itself did not directly lead to excess weight or high blood pressure during adolescence, BMI emerged as the main driver linking prenatal smoke exposure to later health risks, including high blood pressure and obesity.

Researchers suggested the lower risk of excess weight among these adolescents could be linked to poverty and food insecurity — with babies born smaller potentially remaining smaller throughout childhood.

Among adolescents exposed to both cigarette smoke and alcohol in the womb, girls showed notably higher BMI levels and greater body fat measurements than boys — pointing to higher levels of body fat accumulation in girls at this age. The researchers concluded that girls exposed to smoking and alcohol before birth, regardless of whether they were born underweight or overweight, could reduce their risk of future heart and metabolic disease by maintaining a healthy weight. Ongoing monitoring was highlighted as important, as obesity and high blood pressure during adolescence often persist into adulthood. Cardiometabolic risk refers to the likelihood of developing conditions related to both the heart and metabolism — including high blood pressure, obesity, diabetes, heart disease and stroke.

“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.

ALSO: Research examines urban food waste and inequality in Cape Town