High cholesterol from moms smoking?

The notion that small babies are at an increased risk of developing high cholesterol as adults may only hold true for children of moms who smoked during pregnancy, according to a new study.

Increasing evidence points to a link between being born small-for-gestational-age (SGA) - smaller than the norm for the baby's sex and the week of pregnancy during which he or she was born - and having high cholesterol in adulthood, said Xiaozhong Wen of Harvard Medical School, in Boston.

But he and his colleagues wondered whether just certain groups of people born SGA, or in the bottom 10th percentile for gestational age, carried this higher risk.

Could birth size be stealing the spotlight away from coexisting environmental factors that actually trigger this serious condition, which can lead to heart disease and stroke?

For example, maternal smoking during pregnancy is known to be an important determinant of SGA in developed countries, Wen noted.

The study

To shed light on this potential confluence of factors, the investigators studied the birth records and cholesterol levels of 1,370 adults, who were 39 years old, on average.

A total of 345 subjects (25%) reported having high cholesterol. The rate of high cholesterol was 34 percent in adults born SGA and 24% of those born an age-appropriate size.

On closer inspection, the researchers found that only the adults born SGA whose moms smoked while pregnant were at increased risk of developing high cholesterol.

After taking into account other confounding factors, those exposed to a pregnant mom's heavy smoking (at least 20 cigarettes a day) had two and a half times the risk; moderate smoking (between one and 19 cigarettes a day) raised the risk 1.7-fold.

Those who were born SGA to non-smoking mothers were not an increased risk compared to peers born at normal sizes, the researchers report in the journal Epidemiology.

The findings

And the normal sized babies who were born to smoking mothers also didn't appear any more likely to develop high cholesterol compared to those unexposed.

"It seems to be the co-existence of maternal smoking during pregnancy and SGA that put offspring at high risk," said Wen. The researchers acknowledge some limitations to their study, including its observational nature that precludes proving cause and effect, and the small number of participants that were actually born SGA.

While more studies are needed to confirm the potential link, Wen and his team are already planning to expand their research to other adult diseases, such as high blood pressure, heart diseases, stroke and diabetes.

"Besides maternal smoking," he said, "other possible co-factors, such as genetics, nutrition and stress, should also be considered.

"For now, he says the current findings give pregnant women have at least one more reason to stop smoking." (Reuters Health, September 2010)