Smoking during pregnancy cuts the level of good cholesterol in kids, thereby increasing heart attack or stroke risk, says research.
HDL -- or high-density lipoprotein -- cholesterol helps protect against heart disease as one gets older.
The research, published in the European Heart Journal, showed that by age eight children born to mothers who smoked while pregnant had HDL cholesterol levels about 10 percent below normal, once other factors were taken into account.
Whether or not children were exposed to other people's smoke after birth did not change the outcome, a strong indication that prenatal exposure had the most impact on subsequent development, the study found.
"Our results suggest that maternal smoking 'imprints' an unhealthy set of characteristics on children while they are developing in the womb, which may well predispose them to later heart attack and stroke," said David Celermajer, a professor at the University of Sydney and leader of the study.
"This imprinting seems to last for at least eight years and probably a lot longer."
Smoking during and after pregnancy has long been linked to a range of health consequences in offspring, including behavioural and neurocognitive problems, and sudden infant death.
Up to now, however, it was unknown whether pre-natal exposure upped the risk of future cardiovascular disease.
Celermajer and colleagues examined the effects of maternal smoking on the thickness of the arterial wall and the levels of lipoproteins in 405 healthy eight-year-olds born between 1997 and 1999.
The children had been enrolled before birth into a clinical trial looking at asthma and allergic diseases.
The researchers collected data on the mothers' smoking habits during and after pregnancy, and on the children after they were born.
They used ultrasound scans to measure the arterial wall thickness and, in 328 children who agreed, took blood in order to measure lipoprotein levels.
There was no effect on the thickness of the children's arteries, a telltale sign of heart disease.
But levels of HDL cholesterol were lower, suggesting a 10 to 15 percent higher risk for coronary disease later in life for the children of smoking mothers.
The prevalence of smoking during pregnancy is around 15 percent in many Western countries.
"We will have to do long-term follow-up to see if these particular children continue to have lower HDL cholesterol levels than normal, but one should presume that this risk factor might indeed be persistent," said Celermajer.